Board Thread:Questions and Answers (Q&A)/@comment-74.139.152.172-20141212231946/@comment-25870309-20141220032903

Melee. Roll base damage. Add damage enhancement, if applicable. Add strength modifier, if applicable. Add additional damage like elemental, poison etc. which is always a fixed amount.

- In some BG versions, there is another damage bonus for 2-hand weapon.

Range. Same as melee, except ignore strength modifier.

Crits.  Roll base damage twice. Add the enhancements and modifiers to each roll separately, ignoring elemental, poison for all but the initial damage roll.

Backstabs.  Same procedure as crits but re-rolls can be up to 5 times (IIRC).

Spell damage.  Self-explanatory by reading the individual spell descriptions.

To get the NET damage, take the calculated amount and then subtract any damage reduction, damage resistance or damage immunity.

Take note that all this damage calculating assumes a THAC0 high enough to actually hit or else rolling a natural 20. Also, when assessing damage, it is usually more useful to express it in terms of "damage per round" and to factor in APR, Haste effects, HLAs, etc.