How this instrument works
Fifth-edition D&D rates encounter difficulty by comparing two numbers: how much raw experience the monsters are worth, and how much experience your specific party can handle at each difficulty tier. The Dungeon Master's Guide publishes four XP thresholds — Easy, Medium, Hard, and Deadly — for every character level from 1 to 20, and a party's threshold at each tier is just the sum of each character's individual threshold at that level.
Raw monster XP alone understates the danger of a fight, though, because multiple monsters acting together are more dangerous than their individual XP values suggest — they can flank, focus fire, and act more times per round than a single monster of equivalent total XP. The DMG corrects for this with an encounter multiplier that scales up with monster count: a single monster uses a x1 multiplier, but a group of 3 to 6 monsters gets doubled to x2, and larger groups scale higher still. Multiplying total monster XP by this factor gives the adjusted XP that actually gets compared against the party's thresholds.
Comparing adjusted XP against the four party thresholds gives the final call: below Easy is Trivial, at or above Easy but below Medium is Easy, and so on up through Deadly. This is the DMG's own encounter-building heuristic, not a combat simulator — it's meant as a fast pre-fight sanity check, and real outcomes still depend heavily on tactics, terrain, resources already spent, and plain dice luck.
- Enter the party's average character level.
- Enter the number of player characters in the party.
- Enter how many monsters are in the encounter.
- Enter the monsters' total raw XP — the sum of each monster's XP-by-challenge-rating value, before any multiplier.
- Read the party's four XP thresholds, the adjusted encounter XP, and the resulting difficulty rating.
Worked example — a level-5 party against four monsters
A party of 4 characters at level 5 has DMG per-character thresholds of 250 / 500 / 750 / 1,100 XP for Easy / Medium / Hard / Deadly. Multiplied by 4 party members, the party's own thresholds become 1,000 / 2,000 / 3,000 / 4,400 XP.
The encounter itself is 4 monsters worth 450 raw XP combined. Because 4 monsters falls in the 3-to-6 range, the DMG's multiplier is x2, so adjusted XP = 450 × 2 = 900. That 900 falls below even the party's 1,000 XP Easy threshold, so the DMG rates this encounter Trivial — despite four monsters showing up, the fight isn't expected to meaningfully tax the party's resources.
Questions
Why does the number of monsters change the difficulty even when raw XP stays the same?
Because more monsters acting together are tactically more dangerous than one monster with equivalent total XP — they can surround the party, attack from multiple angles, and simply act more times per round. The DMG's encounter multiplier (x1 for one monster, x2 for 3-6, scaling higher for bigger groups) exists specifically to correct for that extra danger, which is why the same 450 raw XP can rate very differently depending on whether it's one big monster or four smaller ones.
Where do the per-level XP thresholds and monster-count multiplier actually come from?
They're published directly in the 2014 Dungeon Master's Guide's encounter-building chapter — a table of four thresholds (Easy/Medium/Hard/Deadly) for every character level 1 through 20, plus a separate multiplier table keyed to monster count. This tool reproduces those official tables exactly rather than approximating them.
Does a Trivial or Easy rating mean the encounter is guaranteed safe?
No — the DMG's difficulty rating is a planning heuristic based on expected resource depletion over a full adventuring day, not a combat outcome simulator. Poor tactics, unlucky rolls, bad terrain, or a party that's already burned through resources earlier in the session can all turn a rated-Easy fight genuinely dangerous, and conversely a well-played party can walk through a rated-Hard fight with a good plan.
What XP value should I use for each monster?
Use each monster's XP-by-challenge-rating value from its stat block or the Monster Manual's CR-to-XP table, then sum those individual values together before entering the total here — that raw sum is what gets multiplied by the monster-count multiplier, not each monster's XP individually.
How is 'average party level' handled for a mixed-level party?
The DMG's own guidance is to average the party's character levels, round down if it lands on a fraction, and use that single average level to look up thresholds for every character — it's a simplification that works well enough for parties within a level or two of each other, but gets less reliable the wider the level spread gets.