Damage calculator

It models base stats with Season 3’s linear growth, spell base damage and ratios, item stats, item passives that change damage (penetration, on-hit, crit multipliers, ability-power multipliers, stat conversions), mastery effects, and the fixed order armour is reduced and penetrated in — reduction, then percent penetration, then flat penetration, with penetration unable to push a resistance below zero.

It does not model range, crowd control, mobility, mana cost, cooldown pressure, or a target that moves. A build that wins here can still be a bad pick, which is why the measured builds carry a written note the arithmetic could not produce. Anything the model cannot read cleanly out of the patch data is flagged on the row rather than quietly counted — hover the badge to see what the encoder could not resolve.

The link at the bottom left encodes the whole setup, so a build can be sent to someone else and it opens exactly as you left it.