If compiled with SHOWDMG defined, then SLASH'EM has an option showdmg to add the amount of damage to the message when monsters hit you. "The newt bites! [2 pts.]" It makes more obvious what your HP counter on the status line already shows. To use this option, remember to enable it.

When your character reaches a certain level, then the showdmg option will also show how much you damage enemies. "You kick it. (3 pts.)" The minimum levels are:

• Barbarian, Monk: Level 10
• Caveman, Valkyrie: Level 12
• Samurai, Knight: Level 14
• All other gnomes: Level 14
• All other races and roles: Level 17
• Any character in wizard mode: Level 1

Source code reference: src/hack.c#line2596