D&D Improvised Numbers to Be a Better and Faster Dungeon Master

Welcome back, reader. Today, we’re talking about D&D improvised numbers for Dungeon Masters. In making and testing my personal DM binder, I kept getting asked if I would put it up on DriveThruRPG/DM’s Guild for others to download.

In a word, no. Because of the nature of the DM binder, it has quite a bit of material that is not my custom homebrew material. That includes work from other D&D personalities, content creators, and official D&D material from Wizards of the Coast.


While WotC has walked back their updated OGL faux pas, I still feel apprehensive from a legal standpoint about publishing anything that directly reflects D&D official content. Even though the basic rules are now free, WotC and Daddy Hasbro have firebombed their relationships and inherent trust with third-party supporters and content creators.

If I don’t think I can publish it as a product, my next best option is to release the information on the blog. I thought I’d walk through some of the more homebrewed sections of my DM binder in blog updates. 

Firstly, it helps disseminate the knowledge to those who want to use it. And second, I’ve already done the bulk of the work. Having a less intensive blog between chunky content related to the worldbuilding process and ongoing DM binder work would be nice.

That’s probably enough hemming and hawing; let’s get into the D&D improvised numbers by improvising DCs for D&D 5e.

D&D Improvised Numbers: Improvising DCs

I’ve explained my 3d6 method for improvising D&D DCs before, so long-time blog readers will be familiar. But, for those new to the blog, let’s review. Improvising DCs is fairly simple. D&D 5e gives us a chart and a basic rule of thumb for creating DCs on the fly. On the very easy side, we’re instructed to set the DC at five. For average difficulty, DC 15, and it caps out with DC 30 as “Nearly Impossible.” It’s a good range, despite “nearly impossible” not being that impossible. By the time an optimized PC hits 5th level they should have a high enough ability modifier and expertise to start hitting DC 30 checks.

D&D 5e DC Rule of Thumb

The go-to example for 5e Dungeon Masters is DC 13-17. Don’t know how difficult something should be? Well, if you use a DC in that range it will generally feel right. So, that’s all you need as a DM. You can use the rule of thumb and transfer that range to the other difficulty levels laid out in the PHB. That’s fine, but I like a little something extra. I like a wider range of DCs in my game. 

For instance, last year I was running a dungeon and I didn’t want the party to easily walk in through the front door of the abandoned dwarf hold. So, I covered it in rime frost and set it to a Strength DC 22 check. They’re a third-level party so the likelihood of them busting through the front door was unlikely. Famous last words. Of course, they roll a natural 20 and kick open the doors, now starting the dungeon in its middle rather than at the start. 

And that’s worth remembering. If you stat it, the PCs can and will beat it. I let them do it because I made it part of the gameplay mechanics. After the session, I told them I wasn’t expecting them to go that way, and they felt great because they made a choice and did it their way, which is what RPGs are all about. 

3d6 Improvised DCs for D&D

However, let’s get back to the 3d6 DC framework. You roll 3d6 like old-school ability score generation. Now, until you’re familiar with improvising the DCs, I suggest using two like-colored dice and one odd-colored die to tell the difference. 

First, you total the like-colored 2d6 and check the chart for the foundational DC. The chart is set up using the 2d6 bell curve, so you’ll usually end up with an average DC in that 13-17 range. Here’s the chart:

2d6 Foundation DC Chart

20, Very Easy
3-45, Easy
5-910, Medium
10-1115, Hard
1220, Very Hard

The last die we use is like an ability modifier, and we add it to the foundational DC. Here’s a quick example. I rolled 3d6 and got 5, 4, and 3. Well, five and four make nine, so that’s a DC 10 foundation. Our last die adds +3 for a total of DC 13. That’s right in the sweet spot. Now, one final adjustment. If the check requires training in a specific tool, skill, vehicle, etc., we double the modifier amount. 

Taking the above numbers, let’s say we need to improvise a DC to stop an out-of-control carriage. Well, if the PC wants to hop onto the driver’s seat and saw the reins to reduce the speed, I don’t think you need land vehicle proficiency to do that. But, if instead the druid wanted to speak with animals and convince the horses to stop, I would say they would NEED animal handling as a trained skill to understand how to communicate effectively with draft horses. So, that DC would go from DC 13 to DC 16. 

This little addition might seem unnecessary, but it’s to pull those PCs with expertise in specific areas back into the normal range of success/failure while still letting them blow DCs out of the water with a high roll. Like in the example above, the Druid should have at least a +5 to that roll, and I’d likely give them advantage if they have a speak with animals ability or burn a spell to do so. That would give them an effective +10 to make the DC 16 roll. They have a 75% chance of success, which feels right for the situation.

Got It, But Why Do It This Way?

Mainly because it keeps me from using the rule of thumb. As a player, when nearly all DCs are in that 13-17 range, you start to metagame. We all do it. We look at our sheet for our bonus and prematurely decide if we will likely make a check before we even attempt it. It leads to things like, “oh, we don’t have a strength-based PC in the party, so we’re not going to be able to break down the door.” Well, for all you (and I!) know, that door’s DC is a four. Maybe it’s full of dry rot, or the hinges are rusted through. 

I want to make a wider variety of DCs in my adventures, and for me, at least, this is best accomplished by randomizing the DCs. But, like any randomizer and improvisation tool, I hold veto power as the human at the helm. Gating something like treasure behind a DC 24 lock-picking check isn’t fun. In that instance, I’ll change the DC to something more reasonable or use it narratively. Failing the check doesn’t mean the party doesn’t open the chest, but it takes a long time to do so. I’ll make a roll on the wandering monsters chart to accompany that failure. 

And I think that’s a good lesson to learn about improvising and random resources in general. Take a second to see if you can make it work in the game before scrapping what you rolled. It involves asking yourself how and why questions, often at the table while playing, but if you can develop this skill you’ll become a much better DM and your games will run smoother as you become more confident in your ability to roll with the punches.

And that’s it for improvised DCs. Go ahead and try them out. It’s been a valuable asset to me, and I can now improvise DCs at the table without reference. In the next section, we’ll discuss the big one, using D&D improvised numbers to create custom monsters. 

D&D Improvised Numbers to Create Custom Monsters

What’s there to say about D&D improvised numbers for monster creation? It is a subject that is done to death. It seems like every D&D 5e content creator has their own method of building with only a single consensus, they’re better than the official rules for building monsters in the Dungeon Master’s Guide. Far from controversial to say D&D 5e’s monster math is a real mess. It’s a tool for creating monsters made by the game’s designers but the official monsters they actually designed for the game don’t match the numbers!

The monster-building tools were definitely a letdown for me in this edition. Especially when compared to 4e’s monster and encounter building math, that edition’s math was tight as a drum and just chef’s kiss to use as a Dungeon Master. I know it’s cool to hate on the edition (it’s definitely not perfect), but it’s so well-tuned at what it does and is such a breeze to run as a DM. Fourth edition, for all the snark of not being D&D enough, is the edition of the game most designed with a DM-first philosophy. 

Anyways, I decided I would toss my own attempt at monster-making rules into my DM’s binder. Now that I’ve used the Book I binder, this is probably a section I’d cut. I might migrate it to the adventure-making section, my DM Binder Book II, because I rarely improvise brand new monsters at the table. I’m likelier to reskin an existing monster from official or third-party material to fit my need. I think it’s just faster to do and easier to run. I can always tinker with the reskinned monster’s stat block between game sessions.

Below is a big chart with a bunch of numbers. I’ll go through each section quickly to explain how those numbers came to be and showcase at least one example of using it. But first, I want to talk about why I created this the way I did and why the numbers look the way they do. I find that most custom monster-building tools are trying to reengineer the existing official monsters to make a rubric for how to create those monsters. The problem is, there’s no consistency because the D&D design team clearly didn’t follow their own ideas for what numbers monsters should have. It’s trying to identify the order of D&D’s monsters when they were designed without order. It’s chaos all the way down.

Instead, I just designed the monsters off of what everything in D&D is actually based on: the player characters. Because, unlike D&D 5e’s monsters, there are actual hard and fast rules on how to create a player character. And, if we base the monsters on what the average PC can do, they should align. Or at least align roughly. 

And there’s no PC more average than the 5e fighter. So, I built the table off the fighter’s progression and used creative math to make it feel right. Therefore a monster created with these numbers should be roughly equal to a PC of the same level. You have a party of four PCs? You create four custom monsters of the same level to oppose them. If you wanted, you could hack the Encounter Quick Matchups table from XGE to help diversify your encounter building using monsters made from the below numbers.

Without further ado, let’s dive in. 

Party Level

Here you find your group’s average party level, which tells you which row to use to make your improvised monster. The range runs from less than one to 21+, so you can create monsters beyond the minimum and maximum player character capabilities.

Improvised Armor Class

We know that most PCs run an armor class somewhere between 11-13 on the low end and the low 20s on the high. Now, if the monster I’m improvising is a humanoid or a war mount, I’d use the standard rules for armor and barding and choose what makes the most sense for the monster. Don’t slap plate armor on bandits or barding on a farmer’s pony.

Improvising AC for non-humanoid monsters is also easy. It’s a base of 10, like normal, then add the monster’s prime ability modifier, and the adventure tier. So, for a <1 monster that would be 10 + 1 + 0 for an average AC of 11. Now you might think, that’s a tad low for even a throwaway mook. I want it higher. Well, there are two ways to do so. First is by looking at your players’ PCs. What is the party’s average to-hit bonus? Add 10 to that and you have a crisp starting point for AC. I also have a note on how to modify the basic numbers, we’ll look at that towards the section’s end.

Monster Hit Points Using D&D Improvised Numbers

Calculate HP with a fairly simple little algorithm based on the average attack damage of the monster. You can roll the damage die or take the average, add the damage modifier, and then multiply the sum by the party level—just a few minor caveats. We can’t get a positive HP total multiplying by zero, and we want to beef our level one and 21+ monsters a bit. For <1 monsters, roll their HP/Damage die w/ disadvantage. For first-level monsters, roll with advantage or max the hit die like you do for PCs. You also roll with advantage for 21+ monsters because they’re typically campaign end bosses so they could use a little extra HP to stay in the fight.

D&D Improvised Numbers for Monster Proficiency and Ability Modifier

These two are listed together because combining them will tell you the to-hit modifier for the monster. The proficiency bonus follows the RAW for 5e fighters, and the ability mod increases align to the levels where PCs gain Ability Score Increases. Where most PCs cannot boost their ability scores above 20, monsters have no such cap. Therefore every few levels they get a little bit better at hitting PCs and hit them a little harder. 

The superhuman ability modifiers are included to help make up for the fact most monsters don’t have special abilities and resources like smite and magic items to increase their damage. Also, because I didn’t want to include the traditional monster attacks with multiple damage dice because PC attacks don’t work like that, and it’s one of the wonkiest and most nonsensical designs of 5e monsters. This monster’s attack does 1d10 damage, and the other does 2d6, but they’re the same CR. The dice have no consistency, so I wanted to avoid making it up whole cloth.

Number of Attacks for Custom Monsters

Again, we’re using the 5e fighter as a guide because most monsters make physical attacks, and that’s the fighter’s specialty. It’s very straightforward, and there’s no derived numbers from the number of attacks. The only point to note is that this will skew away from most monsters if you compare these PL-based monsters to CR-based ones. CR monsters tend to get extra attacks and multiple damage dice early, but that’s because those rubrics don’t align with each other 1-to-1. 

For example, a CR 5 monster is supposed to be equivalent to a 10th level PC. So looking at a CR 5 monster and a PL 5 improvised number monster together, they will look a lot different in their numbers and abilities. Why did D&D make CR go from zero to 30 instead of 1-20 like PC levels? Who knows? Again, why it’s basically pointless to look at a monster’s CR because that ranking by itself tells me nothing about its strength of it or where it fits as a challenge for a party of any level. 

Special Ability/Trait

The last column in the table serves as a guideline for how many special abilities or traits a monster should have. These special abilities and traits don’t include what we would consider inherent or “no-brainer” traits, such as a poisonous spider having a venomous bite, poison immunity, and a climb speed. But, it would cover something like a unique ability to shoot a web at a creature as an attack/ability. So it is vital to consider the type of monster you’re building and what common sense abilities, features, or traits it would have. If you’re making a construct, 5e constructs have a block of specific features that should probably be included and would not count as a unique ability/trait for this circumstance.

You may be wondering: what does constitute a special ability or trait? I like to focus on abilities that give monsters more options and versatility, like adding wings and a fly speed to kobolds, or borrowing the goblin’s Nimble Escape feature. Those are example abilities that give monsters better mobility options and set the latter up as an ambusher who can attack and melt back into areas with lots of cover and obscurement. 

Other types of abilities to consider are ways they can get advantage on foes or buff/debuff abilities, like adding conditions to players. Maybe they have a limited ability that uses the damage formula in the following section. These one-time or recharge abilities with improvised damage are great for grenades, fire breath, or spell-like abilities. For more ideas of traits to add to your monsters, I suggest checking out the monster-building section in the Dungeon Master’s Guide and community resources like Badooga’s Monster Guidelines.

D&D Improvised Numbers for Custom Monsters Table

Party LevelAC (10+Ability Mod+Tier)HP (Avg Atk Dmg*PL)Proficiency/Ability Modifier# of AttacksSpecial Ability/Trait
<111Disadvantage2/11If one remove Prof





















Extra D&D Improvised Number Monster Math & Info

  • Damage per Attack = Weapon OR HP/Magic Die + Primary Ability Mod
  • Ability/Spell Save DC = 8 + Attack Bonus
  • Saving Throw Bonuses
    • 1 = Attack Bonus
    • 1 = Ability Mod
    • 2 = Prof
    • 1 = Ability – Prof
    • 1 = Prof – Tier
  • Limited Damage for limited abilities and spells, NOT basic attacks 
  • Modify: Add up to a +3 to any number but must subtract an equal amount from a different number
  • Thematic & Advantageous Proficiencies/Non-Damage Abilities and Traits

Example Monsters Using D&D Improvised Numbers

To show off the table and how it works, I drafted up a trio of monsters so you can see how the math works and compare it to established monsters of approximate power/challenge rating. 

I think I’ll draft a humanoid, a dragon, and an ooze to show the versatility. Those are pretty different types of creatures, including one that uses arms and armor. I rolled randomly for what party/PC level these monsters should be. So, we’ll be drafting a 5th-level humanoid adversary level (CR 2-3), a 4th-level dragon (CR 2), and an 8th-level ooze (CR 5).

And below are the consolidated stat blocks using the D&D improvised numbers for custom monsters, and I also included similar official monster stat blocks for comparison.

Caustic Wyrm (Dragon 4th Level [CR 2])

AC 15 (Natural) HP 38
Darkvision 60, Fly 60, Large, Draconic
S2 D6 C4 I2 W2 Ch1
– Acid Immune
1 Attack @ +6/1d10+4 (Bite[P], Claw[S], Tail Whip[B])
— Abilities —
Acid Spit [Recharge 5,6]
Range 30, Burst Radius 10
Dex DC 14, 4d6+4 Acid
Compare to Wyrmling stat blocks

Dwarf Heavy Guard (Humanoid 5th Level [CR 2-3])

AC 16 (Scale) HP 68
Darkvision 60, Dwarvish
S7 D3 C4 I1 W3 Ch2
Resist/Adv vs Poison
2 Attacks @ +7/1d10+4 (Battle axe, 2H)
Topple: on hit, Dex DC 15 or knocked prone
1 Attack @ +7/1d10+4 (H Crossbow)
Compare to Berserker and Knight stat blocks

Mini Master (Ooze 8th Level [CR 5])

AC 18 (Natural) HP 68
Blindsight 60, Climb 20, Small, Pass Through 1” Spaces
Stealth +6
S6 D3 C9 I1 W3 Ch3
Immune Blind/Deaf, Charm, Fatigue, Fright, Prone
Resist Non-magical B/S/P
2 Attacks @ +9/1d4+6 (Reach 10)
Sticky: on hit, Str DC 17 or Grappled
— Abilities —
Reaction: When hit by melee attack, apply Sticky
Overcome: Action, moves into grappled creature’s space; on target’s turn, the Slime may command them to move and use their attack action to make all possible basic melee attacks against a target of the Slime’s choice
– While in Overcome, damage to Slime is halved between the Slime and target
– At the end of its turn, Overcome creature can reattempt Str DC 17 to free from grapple
Compare to Adult Oblex and Black Pudding stat blocks

The proof is in the pudding (pun intended!). Use this to create your own custom monsters, and add it to your DM binder. And, to cover all bases, I included a 1:1 table of party-level monsters to the corresponding CR for official monsters to help you build encounters that contain both types of monsters. In the next section, we’ll review improvised damage, like what’s seen in the Caustic Wyrm’s acid spit.

1:1 Monster to PC, Party Level to CR Chart

Party LevelAverage CR

D&D Improvised Numbers for Limited Damage

As with improvising DCs, it’s critical to get a handle on improvising damage as a DM. Being able to dish out damage in any situation quickly is an extremely helpful tool for game mastering. And that works for both sides of the table regarding player hijinks. Sometimes you need to deal damage to the PCs, and other times you need to deal damage FOR them and their wild ideas.

In a D&D game I’m currently playing, one of my friends struggles with this as a DM. They have accidentally killed multiple low-level player characters with situational damage. Situations like a PC failing a battery of skill checks and falling into lava. Or, hitting a low-level character with a Disintegration spell trap, or a party with a high CR red dragon’s breath weapon. It’s important to note in these examples that the challenge is way above that of the party. Also, this wasn’t the group doing something stupid and traipsing off the critical path and getting punished for it. These were part of the main narrative of the adventure. 

I believe this is indicative of the official 5e resources when it comes to D&D improvised damage. I mean, we had to look up lava damage, which by the book, is anywhere between 10d10 and 18d10 damage, depending on how submerged the PC gets. 

That damage is absolutely deadly for low-level parties. Not to mention 5e RAW’s improvised damage is unclear with its 1-24d10 approach broken down by setback, dangerous, and deadly categories. The amounts seem arbitrary, and they’re impossible to memorize. This means a Dungeon Master has to look up the values every time they need to improvise damage and then still figure out what seems appropriate using the book’s examples. 

My D&D Improvised Numbers for Damage

Those who downloaded my Quick Reference sheet from DriveThruRPG already know the answer. I got tired of referring back to the book so that I could then still improvise the damage and instead made my own D&D improvised damage algorithm that’s easy to remember and use. Now, we’re focusing on LIMITED damage when we’re talking improvised damage. 

Limited damage is one-time damage, or rather, it’s not repeated spammable damage like monster attacks or persistent traps and hazards where a PC is likely to take the damage multiple times in the same scene. Doing so WILL probably kill one or more PC. We want to balance the damage so it will almost take a PC from max to zero HP, not straight-up kill them. Like the rest of 5e’s design philosophy, we want to avoid Save-or-Die situations. 

We begin the process with targeting. Is this damage that will affect one PC, or is it a multi-target/area of effect damage? The answer depends on what size damage dice we use. Multiple targets/AoE effects roll six-sided dice. This decision ensures significant damage spread across the PCs but is unlikely to KO PCs with most of their hit points, or hit the negative HP threshold to kill them outright. For single-target damage, we use a ten-sided die. The large die size increases the tension as the damage is more likely to KO or significantly deplete the hit points of most classes (d6 and d8 hit dice).

The algorithm is easy to remember and use, with no chart necessary, and scales with party level. The scaling ensures I’m not accidentally throwing 10-18 d10 at a third-level PC and killing them outright.

  • One Target: Xd10+X Damage
  • Multi-Target: Xd6+X Damage
    • X = Average Party Level 

It’s much easier to remember and use without stopping to look up damage. I thought I’d rework the examples from my friend’s game above to show it in use.

Disintegrate Spell Trap

Very simple to do, it’s a third-level party, and the trap is a one-and-done focused on a single creature’s interaction. So, I would make the damage for the trap 3d10+3. Now, I would also want to retain the grim lethality of the Disintegrate spell so if it happens to reduce the target to zero HP, the spell rules for Disintegrate are in effect. Lethal, but the likelihood that an average of 20 damage on a failed save will wipe a third-level PC is much lower than the original. 

Plus, even if it does dust a PC, it’s a lot more memorable when they get disintegrated due to 1-2 points of damage and not the average 75 force damage the original spell usually does. A third-level PC cannot survive that regardless of its current hit points.

Lava Hazard

This lava was a hazard encountered by our 4th level party and was a significant hazard all the PCs needed to cross, so multi-target for sure. The scene worked as a mini skill challenge where each PC needed to make three checks to cross the chamber. First, this breaks the limited damage aspect of our D&D improvised damage rules, so we’ll need to work around it. Second, a valuable bit of DM advice, the more checks you require to do something, the greater the likelihood of failure for the PCs. 

Well, with this D&D improvised damage algorithm, it’s 4d6+4. Well, that will have a high mortality rate if a PC fails three times in a row. Instead, I will actually up the damage total and then segment it. I’ll change it to 6d6+6 and then break it into three potential 2d6+2 damage areas, one per check needed to cross the room. 

There were opportunities to heal while crossing the room, so the upscaled damage shouldn’t be lethal so long as the party plays smart. As a DM, it’s essential to let your players fail too. Look, if your fourth-level PC takes 14 damage from the first of a clear three-check challenge and chooses not to heal, I can’t help you. You know the check to make, the likelihood of your success, and what amount of damage you’re facing. If the second or third failed check sees your PC’s body sink into the lava, that’s just the way it is. As a DM, I’ll protect players from ignorance but not stupid decisions.

Dragon Breath Weapon

Those who read the above section know I often use the D&D improvised number damage framework for limited monster abilities, like a dragon’s breath weapon. For the situation in question, it was a fifth-level party, and a breath weapon is meant to target multiple creatures when possible. That means our damage output for the breath weapon is 5d6+5. 

Experience helps a lot here because I know the party can take the damage no problem, once, but the breath weapon is on a recharge. Dishing out that damage two or three times in combat due to unlucky recharge rolls, and I can accidentally smoke a party fast. So, depending on how devastating the initial breath weapon was, I’d scale it back to 4d6+4 or even 3d6+3 in damage. 

Another tried and true DM method is to fudge. A veteran DM will often “forget” to roll for the breath weapon recharge if the party is on the ropes at the end of round one, much like our original party was in this example. And that’s not entirely on the DM. There was plenty of opportunity, but no one, outside my PC, thought to buy/use an item to grant fire resistance before fighting a red dragon. Again, DMs protect against ignorance, not stupidity. That being said, the damage for the dragon was too high for the party to succeed in the fight realistically, which is why I would improvise it.

And that’s it when it comes to my system for improvising damage in D&D 5e. I’ve found it very versatile and easy to remember, and it keeps me from looking up damage charts and keeps the game flowing. Now, in the examples, I was using DM-to-PC damage, but it works just the same for the opposite. 

If the PCs devise a crazy scheme or trick to use the environment to damage a monster or clever use of spell craft, I’ll use the same D&D improvised damage algorithm. And, because the damage scales, it rewards my players for trying new and different things other than making a weapon attack or casting a cantrip every round.

Wrapping Up D&D Improvised Numbers

Well, that’s all for D&D improvised numbers, the first dive into what custom homebrew content I included in my personal DM binder. I hope you found it helpful. If you want me to cover a specific topic, you can comment below, email me through Gmail @RedRaggedFiend, or send me a Twitter message.

Thanks again for reading. If you’d like to support the blog, I’d welcome the help. You can do so by sharing this post and other topics you’ve found helpful on social media, Reddit, and your RPG forum of choice. If you have an extra dollar or two, check out my PWYW titles on DriveThruRPG or consider sponsoring me through Ko-Fi for just a dollar a month. Speaking of, I should come up with a higher backer tier on Ko-Fi with a reward or two. Do you have any ideas for a backer reward? 

Let me know! Also, a little announcement. 

After some peer pressure from friends, I’m trying my hand at streaming over on Twitch.tv/RedRaggedFiend. Right now, I’m creating a small sandbox and player character to run some solo D&D. So if that sounds like something you’re interested in, go check out the stream and drop me a follow! 

Leave a Reply

Your email address will not be published. Required fields are marked *