How do you calculate damage for MM1 and MM2 monsters?

Question

I realize this may be a subjective question, but I'd really like to know what the consensus is. I know that WotC changed the way they calculate monster damage from MM3 and onwards, but there's isn't much errata for the first books. So:

Do I use the old damage values?

Do I completely recalculate the numbers based on their tables?

Do I double the non-rolled damage?

Do I use some other method?

Answer 1

Sly Flourish has created a cheat sheet that handles adapting every monster-by-level both for damage and HP.

You might also want to see his posts: 4e Damage Dice Calculator and Tools of the Lazy Dungeon Master

Here's an excerpt:

Lvl Low DC Med DC High DC Low dmg Med dmg High dmg High Ltd dmg Minion dmg Avg AC Avg Def Low HP Med HP High HP  Atk vs AC Atk vs Def
1      8      12     19    1d6+3   1d8+4  1d8+6     1d8+8             5      16      14      24     30     38        +6        +4
2      9      13     20    1d6+4   1d8+5  1d8+7     1d8+9             5      17      15      30     38     48        +7        +5
3      9      13     21    1d6+5   1d8+6  1d8+8     1d8+10            6      18      16      36     46     58        +8        +6

Update: In A Suite Alternative, WotC's Chris Perkins also includes a similar table of monster damage, including dice alternatives:

Answer 2

Depends on whether you're wanting to use MM1/2 monsters or make new ones.

If you're looking to use MM1 & MM2 monsters with little or no work converting them, then you want to divide their HP and multiply their damage (all of it, not just rolled) by 1.5 or 2. My experience has been that that MM3 is actually around a 1.67 to 1.75, but that's a lot harder to calculate in a hurry. A 1.5 is obviously going to make things feel closer to the old style and be less of a shock to your players, while a 2 is going to make combat very fast and deadly, and might not be a good idea if your players aren't running relatively optimized builds (my DM specifically allowed people to rebuild their characters a fair amount to account for the change after a session or 2 of trying it out).

If you're making new monsters, you can use the errata-ed monster creation tables found here (warning: that goes directly to a PDF); that should bring the DMG monster creation in line with the MM3 monsters.

Alternately, you can use the tables from that PDF and the damage expressions here which have been specifically maintained to keep monster damage high through level 30 (normally monster damage as a % of player HP drops as the players gain levels, with the most powerful damage expression, limited, going from about 55% of player HP at level 1 to about 33% of player HP at level 30).

Above all, remember that MM3 increased monster damage and reduced monster health. If you use the updated MM3 damage expressions but the old MM1/2 health values, you're making the monsters harder than they're intended to be.