Work out what a weapon does to a target: expected hits, wounds, damage and models slain, plus the odds of killing at least so many. Modifiers, re-rolls, cover and invulnerable saves included.
Pick an attacking datasheet and one of its weapons, pick a target, and the calculator resolves the whole attack sequence: the hit roll, the strength-versus-toughness wound roll, armour and invulnerable saves, Feel No Pain, and how the damage falls across the target unit’s models.
Torrent, Sustained Hits, Lethal Hits, Devastating Wounds, Twin-linked, Anti-X, Melta, Rapid Fire, Blast, Heavy, Lance and Ignores Cover are all taken into account, and anything the calculation leaves out is named alongside the result.