One of the best “features” to ever come out of D&D 4th Edition was this blog post by Blog of Holding that distilled the “monster math” of that game down to a short formula that a DM could draw upon at a moment’s notice. In the interest of trying to recapture some of that convenience, I tried to do a rough approximation of how one might do the same for 5th Edition, based on my earlier work.

To cut right to the chase, here it is:

monster AC = [10 + halfPlayerLevel]

monster HP = [10 x playerLevel]

monster attack rolls = [d20 + halfPlayerLevel]

monster damage-per-round = [2 x playerLevel]

“bad” monster saving throws and ability checks = [d20 + halfPlayerLevel]

“good” monster saving throws and ability checks = [d20 + halfPlayerLevel + proficiencyBonus]

monster ability/spell DC = [10+halfPlayerLevel] (as a cap/max)

As an example of this formula’s output, if you were DMing for a party of level 6 players, then a single monster would look like something like:

13 AC

60 HP

d20+3 attack rolls

12 damage per round (possibly split over two attacks of 1d6+3 each)

d20+3 saving throws for “bad” saves (such as Dexterity or Intelligence on a Fighter)

d20+6 saving throws for “good saves (such as Strength or Constitution on a Fighter)

DC 13 to save against abilities and spells (assuming this is the “best possible”, such as a Wizard’s Intelligence+proficiency spellcasting)

And then you might have one such monster per player, and that would be an “average” difficulty fight.

Feedback I’ve received suggests that the damage and HP figures might be a little on the low side depending on party composition and player skill, so feel free to increase them by as much as double for one or the other, or even both.