D&D CR Calculator - Defensive & Offensive CR, Encounter XP

Q: Should I use Attack Bonus or Save DC for my monster?

Use Attack Bonus if your monster mostly hits things with claws, bites, or weapons. Check the Save DC box for spellcasters, oozes, and anything that mostly forces saving throws, like a breath weapon or an aura. If your monster does both, leave the box unchecked. The tool scores both and uses the higher one.

Q: How do I count a breath weapon or a spell that only works once?

Put it in the Secondary Damage box for the round it is used, not the Primary box. Primary damage is what the monster does every single round. Secondary is one-time or recharge stuff. A dragon might put 50 in Round 1 Primary and 60 in Round 1 Secondary for its breath.

DnD CR Calculator

Updated Aug 20, 2026 By Jehan Wadia

Introduction

Challenge Rating (CR) tells you how tough a monster is. This D&D CR Calculator works out the Challenge Rating for any monster you make. Type in its hit points, Armor Class, damage, attack bonus, and save DC, and the tool does the math for you.

The calculator uses the same steps as the Dungeon Master's Guide. It finds a Defensive CR from HP and AC, then an Offensive CR from damage per round and attack bonus or save DC. It averages the two and adds points for special stuff like legendary actions, lair actions, and traits such as Pack Tactics or Magic Resistance.

You also get:

A full CR 0–30 table you can click to load starting numbers
Auto HP math from size, hit dice, and Constitution
An attack routine builder and spell damage helper
Charts and a step-by-step solution so you can see the math
An encounter check that tells you if the fight is easy, medium, hard, or deadly for your party

Turn on Compare Two Builds to test two versions of the same monster side by side. Use it to balance homebrew monsters fast, so your players get a fair fight instead of a one-hit wipe. Once your monster is finished, run the whole fight through the DnD Encounter Calculator to check the XP budget against your party, and use the Point Buy Calculator when you build the characters facing it.

How to use our D&D CR Calculator

Enter your monster's hit points, armor class, damage per round, attack bonus, and save DC, plus any special traits. The D&D CR calculator gives you a Defensive CR, an Offensive CR, a final Challenge Rating with XP, step-by-step math, and a quick encounter difficulty check.

Target CR Range: Pick the tier you are building for (CR 0–4, 5–10, 11–16, or 17–30). This sets the proficiency bonus used in suggestions.

Expected CR (anchor): Choose the CR you think your monster should be. The tool shows the expected AC, attack bonus, and save DC for that CR.

Ability Scores (STR, DEX, CON, INT, WIS, CHA): Type the six scores from your stat block. The tool suggests an attack bonus and a save DC you can apply with one click. If you are still assigning those scores, the Point Buy Calculator handles the spend for you.

Size: Pick Tiny through Gargantuan. This sets the hit die (d4 up to d20) and re-figures average HP.

Hit Dice Count: Enter how many hit dice the monster has. HP is figured from dice, die size, and CON. The Dice Average Calculator is handy if you want to check the mean roll of any dice pool by hand.

Constitution Score: Enter CON here or in the ability score box. Both stay in sync and feed the HP total.

Average HP: Auto-filled from size, hit dice, and CON. You can type your own number instead.

Armor Class: Enter the AC on the stat block. Every 2 points above or below the expected AC moves Defensive CR one step.

Resistances / Immunities: Choose None, resistances, or immunities to common damage types. This raises effective HP based on the CR band.

Vulnerable to common damage types: Check this box if the monster takes double damage from bludgeoning, piercing, or slashing. It cuts effective HP in half.

Defensive Traits: Check any that apply, like Magic Resistance, Legendary Resistance, Regeneration, or Undead Fortitude. Some ask for a number, such as uses per day or HP healed each round.

Primary Damage (Rounds 1–6): Enter the average damage the monster deals every round from its normal attacks. Only rounds 1–3 count toward the average. If you want a sustained damage figure to compare against, try the DPS Calculator.

Secondary Damage (Rounds 1–6): Enter limited-use damage for that round only, like a breath weapon or a spell. Count area attacks as hitting 2 targets.

Build Attack Routine: Add each attack with its name, attack bonus, dice, die size, damage mod, and uses per round. Then click apply to send the total to Round 1 Primary damage.

Spell Slot DPR Assistant: Pick the spell level, number of dice, and die size. Click apply to fill Rounds 1 and 2 secondary damage.

Attack Bonus: Enter the monster's best to-hit bonus. Every 2 points off the expected number shifts Offensive CR one step. The Dice Probability Calculator shows how often that bonus actually beats a given AC.

Save DC: Enter the DC of the monster's main save-based power. It is scored the same way as attack bonus.

Uses Save DC instead of Attack Bonus: Check this for casters and monsters that mostly force saves. The tool then scores Offensive CR from the save DC only.

Offensive Traits: Check traits like Pack Tactics, Frightful Presence, Constrict, or Possession. These add to attack bonus, save DC, or multiply Offensive CR.

Special Features: Check Lair Actions, Legendary Actions (and how many), Innate Spellcasting, or Multiattack Efficiency. These change the final CR after the average is taken.

Number of this monster: Enter how many of them show up in the fight. This sets the raw XP and the encounter multiplier.

Number of player characters: Enter your party size. Small parties raise the difficulty and big parties lower it.

Average player level: Enter the party's average level. The tool compares the adjusted XP to the easy, medium, hard, and deadly thresholds. For mixed groups of different monsters, move over to the DnD Encounter Calculator.

CR Reference Table: Click any row to load that CR's expected AC, attack bonus, and save DC as your starting point.

Compare Two Builds (A / B): Turn this on to build two monsters side by side and see how their Challenge Ratings differ.

What Is Challenge Rating (CR) in D&D?

Challenge Rating is a number that shows how tough a monster is in Dungeons & Dragons 5th Edition. A CR 1 monster is a fair fight for four players at level 1. A CR 10 monster is a fair fight for four players at level 10. CR goes from 0 up to 30, with small steps like 1/8, 1/4, and 1/2 for weak creatures.

Why CR Matters

CR helps a Dungeon Master pick monsters that fit the party. Pick a CR that is too low and the fight ends in one round. Pick a CR that is too high and the players may die. CR also tells you how much XP the monster is worth, so you can plan how fast the party levels up.

The Two Halves of CR

Every monster has two scores that get averaged together:

Defensive CR — how long the monster stays alive. This comes from its hit points and Armor Class. Traits like Magic Resistance, Legendary Resistance, damage resistances, and regeneration make the monster harder to kill, so they raise this score.
Offensive CR — how much hurt the monster deals. This comes from its damage per round plus its attack bonus or save DC. Traits like Pack Tactics or Frightful Presence push this score up.

You add the two numbers and divide by 2. That gives the final CR. If you want to double-check that midpoint on its own, the Average Calculator does it in one step.

Effective vs. Actual Stats

The rules use "effective" numbers, not just the numbers printed on the sheet. A monster with 150 HP and resistance to common damage feels much tougher than 150 HP, so its effective HP is higher. The same idea works the other way: a monster that takes double damage from swords has lower effective HP. AC works this way too. Strong saving throws or a Parry reaction act like extra AC.

How Damage Per Round Is Measured

Damage is checked over the first three rounds of a fight, then averaged. Use average dice values instead of rolling — the Dice Average Calculator gives you the mean of any dice expression fast. Ignore critical hits and ignore whether attacks hit or miss. Big one-time powers, like a dragon's breath weapon or a spell slot, only count in the round they are used. For area attacks, count them as hitting two targets that both fail their saves. If you want the real odds behind a save or a to-hit roll, the probability calculator covers it.

Extra Features That Bump CR

Some abilities do not fit neatly into damage or hit points, so they change the final CR directly. Lair Actions add +1. Legendary Actions add about +0.5 for every three actions. Innate spellcasting that deals damage multiplies the Offensive CR.

CR Is a Guide, Not a Law

CR is math, and math cannot see everything. Terrain, party tactics, magic items, and how many healing spells the party has left all change how hard a fight feels. Two monsters with the same CR can play out very differently at the table. Use CR as a starting point, then trust what you see in play and adjust hit points or damage next time. Once the numbers are set, the DnD Encounter Calculator is the fastest way to sanity-check the whole session's XP budget.

Formulas used

Average HP from Hit Dice and Constitution

\text{HP} = \left\lfloor n_{HD} \times \frac{d+1}{2} + n_{HD} \times \left\lfloor \frac{\text{CON}-10}{2} \right\rfloor \right\rfloor

Effective HP (defensive multipliers and flat bonuses)

\text{HP}_{eff} = \text{round}\left(\text{HP} \times M_{def} + F\right), \quad M_{def} = \prod m_i,\; F = \text{Regen} + \text{round}(0.1 \times \text{HP})

Effective AC and CR shift from AC (2 points = 1 CR step)

\text{AC}_{eff} = \text{AC} + \sum b_i, \qquad \Delta_{CR} = \operatorname{trunc}\left(\frac{\text{AC}_{eff} - \text{AC}_{exp}}{2}\right)

Average damage per round (three-round average)

\text{DPR} = \frac{\sum_{i=1}^{3}\left(P_i + S_i\right)}{3}

Attack routine average damage

\text{Dmg}_{avg} = \sum_{k} \left( n_k \times \frac{d_k+1}{2} + \text{mod}_k \right) \times u_k

Offensive CR after trait multipliers

\text{CR}_{off} = \text{CR}_{base} \times \prod m_j, \qquad \Delta_{CR} = \operatorname{trunc}\left(\frac{X_{eff} - X_{exp}}{2}\right)

Final Challenge Rating

\text{CR}_{final} = \frac{\text{CR}_{def} + \text{CR}_{off}}{2} + \sum A_k

Adjusted encounter XP

\text{XP}_{adj} = \text{round}\left(N \times \text{XP}_{CR} \times \mu\right)

Frequently asked questions

Why is my final CR different from the CR I picked as my anchor?

The Expected CR is only a benchmark. It tells the tool what AC, attack bonus, and save DC a monster at that level should have. The final CR comes from your real numbers: hit points, AC, damage, and traits.

If your final CR is higher than your anchor, your monster is stronger than you planned. Lower means it is weaker. Tweak HP, AC, or damage until the two match.

Why do rounds 4, 5, and 6 not change my damage average?

The Dungeon Master's Guide only measures damage over the first three rounds of a fight. Most fights are over by then.

Rounds 4 to 6 are there so you can plan out a longer fight and see the shape of your damage on the chart. They do not count toward the average or the Offensive CR.

Should I use Attack Bonus or Save DC for my monster?

Use Attack Bonus if your monster mostly hits things with claws, bites, or weapons.

Check the Save DC box for spellcasters, oozes, and anything that mostly forces saving throws, like a breath weapon or an aura.

If your monster does both, leave the box unchecked. The tool scores both and uses the higher one.

How do I count a breath weapon or a spell that only works once?

Put it in the Secondary Damage box for the round it is used, not the Primary box.

Primary damage is what the monster does every single round. Secondary is one-time or recharge stuff. A dragon might put 50 in Round 1 Primary and 60 in Round 1 Secondary for its breath.

Why did my HP number change when I typed something else?

Average HP fills in on its own from Size, Hit Dice Count, and Constitution. If you change any of those three, it recalculates and overwrites what you typed.

To use your own HP, type it in the Average HP box last and do not touch the size, dice, or CON fields after that.

Why do resistances give less bonus at high CR?

Because high-level players have ways around them. At CR 4 and below, resistance doubles effective HP. From CR 5 to 10 it is 1.5x. From CR 11 to 16 it is 1.25x. Above CR 16 it gives no bonus at all.

High-level parties have magic weapons and spells that ignore resistance, so it stops mattering as much.

What counts as an area attack and how do I enter it?

An area attack is anything that hits a zone, like a fireball, a cone of cold breath, or a slam that shakes the ground.

Count it as hitting 2 targets who both fail the save. So if your breath does 45 damage, enter 90 in the Secondary Damage box.

Why is my Fly Speed + Ranged Attack trait not adding anything?

That bonus only works at CR 9 and below. Above CR 9, the tool turns it off and shows a note.

High-level parties all have flight, ranged attacks, or long-range spells. Staying in the air stops being a real defense at that point.

Should I check Multiattack Efficiency?

Usually no. Multiattack damage is already counted in your damage per round numbers, so checking the box counts it twice.

Only check it if spreading attacks gives a real tactical edge, like hitting three different players at once or triggering a grapple plus a bite.

How much does a Legendary Action add to CR?

Every three legendary actions add +0.5 to the final CR. Three actions is +0.5. Six actions is +1.0.

This is added after the Defensive and Offensive CRs are averaged, since acting on other people's turns does not fit neatly into damage or hit points.

What does the 2-point rule for AC and attack bonus mean?

Every 2 points your AC is above or below the expected AC moves your Defensive CR up or down one step.

Example: at CR 7 the expected AC is 15. If your monster has AC 19, that is 4 points over, so Defensive CR moves up 2 steps. The same rule works for attack bonus and save DC on the offensive side.

Why is Defensive CR so different from Offensive CR?

That means your monster is lopsided. A high Defensive CR and low Offensive CR is a damage sponge that takes forever to kill but barely hurts anyone. The other way around is a glass cannon.

Both are valid designs, but the averaged CR hides the problem. Try to keep the two within 2 or 3 CR of each other for a balanced fight.

What is the Attack Routine builder for?

It does the damage math for you. Enter each attack's dice, die size, damage mod, and how many times it is used per round. The tool works out the average damage.

Click Apply total to Round 1 Primary to send the number straight into your damage table. Then copy it into rounds 2 and 3 if the monster repeats the same routine.

Can I save or print my monster build?

There is no save button, so write your numbers down or take a screenshot before you leave the page.

You can print the page. The buttons, tables, and input boxes are hidden in print mode, so you get a clean sheet with the CR breakdown, the final result, and the step-by-step math.

How do I use the Compare Two Builds mode?

Flip the switch at the top. A second full monster builder appears next to the first one.

Build your monster in A, then make a changed version in B with more HP or less damage. Compare the two final CRs side by side. Clicking a row in the CR table applies to whichever build you last clicked in.

My encounter says Deadly but my players won this easily. Why?

The XP math cannot see the table. Party tactics, magic items, good terrain, and a full stock of spell slots all make fights easier than the numbers say.

Action economy matters too. One big monster against five players usually loses, even at a Deadly XP total. Use the label as a warning light, not a rule.

What does the encounter multiplier do?

More monsters means more turns and more attacks, so a group is harder than its raw XP suggests. The multiplier bumps the XP up to match.

Two monsters use 1.5x. Three to six use 2x. Seven to ten use 2.5x. Party size shifts it too: under 3 players moves it up one step, over 5 players moves it down one step.

Does the calculator work for D&D 2024 rules?

The tables and math follow the 2014 Dungeon Master's Guide method, which is the most tested CR system out there.

The 2024 monster stat blocks tend to hit harder for their CR. If you are building for 2024 games, bump your damage per round toward the top of the band for your target CR.

What proficiency bonus should my monster have?

It matches the final CR. CR 0 to 4 uses +2. CR 5 to 8 uses +3. CR 9 to 12 uses +4. CR 13 to 16 uses +5. CR 17 to 20 uses +6, and it keeps climbing to +9 at CR 29 and 30.

The tool shows the correct bonus under your final CR result.

Why does the tool ignore whether attacks hit or miss?

The official method keeps damage and accuracy as two separate checks. Damage per round sets a base CR, then the attack bonus adjusts it up or down.

If you folded hit chance into the damage, you would count accuracy twice. Just enter raw average damage as if every attack lands, and skip critical hits too.

How do I build a monster with legendary resistance the right way?

Check the Legendary Resistance box and set the uses per day. Each use adds +1 to effective AC.

Three uses is standard for a boss. That is +3 effective AC, which can push Defensive CR up more than one step. Only give it to solo bosses, not to monsters that show up in groups.

What is the difference between Effective HP and Average HP?

Average HP is the plain number on the stat block. Effective HP is that number after traits are applied.

Regeneration adds flat HP. Undead Fortitude multiplies by 1.5. Resistances multiply based on the CR band. Vulnerability cuts it in half. Only Effective HP is used to find your Defensive CR.

Can I build a CR 0 or CR 1/8 monster with this?

Yes. The tool covers CR 0 through CR 30, including the fractional steps of 1/8, 1/4, and 1/2.

For tiny critters, set Size to Tiny or Small, use 1 or 2 hit dice, and keep damage under 5 per round. Rats, bats, and goblins all land in this range.

Why did my Offensive CR jump so much after checking one trait?

Some traits multiply instead of add. Possession is 1.5x. Constrict, Damage Transfer, and Innate Spellcasting are each 1.25x.

Multipliers stack, so checking two of them can nearly double your Offensive CR. Check only the traits your monster really has.

How do I make a spellcaster monster?

Check the Uses Save DC instead of Attack Bonus box first. Then use the Spell Slot DPR Assistant: pick the spell level, dice count, and die size, and apply it to Rounds 1 and 2 secondary damage.

Add lower-damage cantrip attacks to your Primary Damage for every round. Check Innate Spellcasting under Special Features if the monster casts without slots.