Free 5e tools for players and GMs

DnD CR Calculator

Enter a monster's hit points, AC, damage and attack bonus to estimate its Challenge Rating.

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This free DnD CR calculator estimates the Challenge Rating (CR) of a 5e monster from four numbers: hit points, Armor Class, damage per round, and the attack bonus or save DC of its main damaging action. It runs in your browser, needs no account, and uploads nothing, so you can use it on a phone at the table or while building an encounter. Enter your own monster or load any SRD stat block, and the tool returns an estimated CR, a likely range, the XP and Proficiency Bonus for that CR, and the six nearest SRD monsters to compare against. Use it as a challenge rating calculator for a quick starting point, then adjust for the abilities the estimate does not read.
Dnd cr calculator example

How to use the CR calculator

  1. Enter the monster’s Hit Points.
  2. Enter its Armor Class.
  3. Enter Damage per round: the average damage if every attack hits, with all attacks from one turn added together. For a Multiattack, add the attacks up. For example, two Rend attacks of 14 damage each make 28.
  4. Set ‘Offence is based on’ to Attack bonus or Save DC, depending on how the monster’s main damaging action works.
  5. Enter the attack bonus or DC of that main damaging action.
  6. Read Estimated CR N and the likely range, such as “CR 5 to 8”.
  7. Check the XP and Proficiency Bonus shown for that CR.
  8. Compare the two partial estimates, one from hit points and AC and one from damage and attack bonus. A large gap between them tells you the monster is unusual in one area.
  9. Look through the six nearest SRD monsters and their numbers to sanity check the result.

To try the tool first, select ‘Fill in from an SRD monster’ to load a real monster’s numbers. The defaults are 90 HP, AC 15, 30 damage per round, and +7 attack, which give CR 6 with a likely range of 5 to 8. Select Copy link to keep your numbers so you can return to them or share them.

How do I calculate a monster’s CR?

The tool does not use a formula you apply by hand. It fits a straight line from the numbers in the SRD 5.2.1 stat blocks to each monster’s printed Challenge Rating. It builds two fits, one from the natural log of hit points and AC and one from the natural log of damage per round and attack bonus, then averages them.

Damage per round is read from each stat block’s action text. A Multiattack is added up, otherwise the best single action counts, and a damaging saving throw such as a breath counts in full for one target. A save DC minus 8 gives the same number as an attack bonus, which is why the two inputs can be swapped.

Is this the official CR table?

No. This is D20 Desk’s own estimate, not an official table. The Dungeon Master’s Guide table is not used at all. The estimate comes only from the SRD 5.2.1 stat blocks, so it reflects the patterns in those monsters rather than official rules.

How accurate is the estimate?

On the 338 SRD stat blocks that could be read, the estimated range contains the printed CR for 281 of them, or 83.1%. When each monster is estimated by a model built without it, the rate is 82.8%. The page repeats the first check live each time it loads; the second figure comes from the site’s tests.

The range is wide, because it is about one standard deviation of the fit. A CR 3 Owlbear, with 59 HP, AC 13, 28 damage per round, and +7, gives CR 5 with a range of 3 to 7, which contains its printed CR. A Troll, with 94 HP, AC 15, 33 damage per round, and +7, gives CR 7 with a range of 5 to 8, and its printed CR is 5, the bottom of that range. About 17 in every 100 monsters fell outside their range in testing.

What do I do with the estimated CR?

Treat the CR as a starting point and test the monster in play. The tool ignores special abilities, spells, resistances, immunities, legendary actions, and lair actions, so any monster whose power depends on those needs your judgment. Compare the result with the six nearest SRD monsters, and move the CR up or down when the monster’s abilities clearly add or remove danger.

Frequently asked questions

Can I enter a Save DC instead of an attack bonus?

Yes. Set ‘Offence is based on’ to Save DC and enter the DC. A save DC minus 8 gives the same number as an attack bonus, so a DC 15 is read the same way as +7.

Does the calculator account for spells or legendary actions?

No. It ignores special abilities, spells, resistances, immunities, legendary actions, and lair actions. Adjust the result by judgment and test the monster in play.

Why is my monster’s estimate outside the range?

The range is about one standard deviation, and about 17 in every 100 SRD monsters fell outside it in testing. An outside result usually means the monster’s power comes from something the tool does not read, such as an ability or spell.

Does it work on a phone, and can I save my numbers?

Yes. The tool is free, needs no account, uploads nothing, and works on a phone. Select Copy link to keep the numbers you entered.

Where do the numbers come from?

From the SRD 5.2.1 stat blocks only. The tool reads each monster’s hit points, Armor Class, attack bonus or save DC and damage from the text, and nothing is taken from other books.

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