Maximum Resistances

Compare uncapped Resistance with maximum Resistance. Effective Resistance is the lower of those two values, subject to other current effects. If you have 75% Fire Resistance and raise maximum Fire Resistance from 75% to 80%, you still have 75% effective Fire Resistance until you gain another 5% ordinary Fire Resistance. Against 1,000 Fire Damage, 75% leaves 250, 80% leaves 200, 85% leaves 150, and 90% leaves 100 before other mitigation.

The default maximum is 75%

Fire, Cold, Lightning, and Chaos Resistance each have a default maximum of 75%. The character can have more uncapped Resistance, but only the amount up to the current maximum reduces damage.

The hard cap is 90%

Maximum Resistance cannot be raised above 90%. A modifier that would take a maximum beyond 90% provides no effective cap above that limit.

Maximum and current Resistance are separate

A higher maximum changes the ceiling only. Raising maximum Fire Resistance from 75% to 80% while the character has 75% uncapped Fire Resistance leaves the effective value at 75%. Another 5% ordinary Fire Resistance is needed to reach the new cap.

Uncapped Resistance can exceed the maximum

The character sheet can show the uncapped value in parentheses. Resistance above the current maximum does not reduce more damage, but it can preserve the capped value after Exposure, curses, area penalties, or other Resistance reductions.

Overcap is the excess above the maximum

With 110% uncapped Fire Resistance and a 75% maximum, the character is capped at 75% and has 35 percentage points of overcap. A 20% Fire Resistance reduction would leave 90% uncapped and still 75% effective.

Resistance can become negative

A negative effective Resistance increases damage taken from that damage type. At minus 20% Fire Resistance, a 1,000 Fire Damage amount becomes 1,200 before other mitigation.

Elemental does not include Chaos

Maximum Elemental Resistances refers to Fire, Cold, and Lightning. It does not change maximum Chaos Resistance unless the modifier explicitly includes Chaos or all four Resistances.

Each extra point near the cap matters more

Moving from 75% to 80% Resistance reduces the remaining damage from 25% to 20%, which is 20% less damage taken than at 75%. Moving from 85% to 90% reduces the remaining damage from 15% to 10%, which is about 33.3% less than at 85%.