How much damage does fire do?
Solution 1:
Assuming you mean Afterburn, which is the amount of fire damage you suffer after the flame thrower/flare's initial damage, assuming it is no longer directly hitting you:
Degreaser is 2 damage/half second for 10 seconds (40 total if not extinguished). If a player is jarated, it does 3 damage/half second.
All other flamethrowers, flare guns, lit arrows, or the Cow Mangler 5000's charged shot are 3 damage/half second for 10 seconds (60 total if not extinguished). If a player is jarated, it does 4 damage/half second.