Tenacity

 Tenacity (or Crowd Control Reduction) is a stat that reduces the duration of all incoming crowd control status effects except airborne, drowsy, kinematics, nearsight, stasis, and suppression. The stat is the percentage by which the duration is reduced. The duration cannot be reduced below 0.3 − 0.625 seconds (based on when the game adds / removes the buff). The duration of the crowd control is calculated at the time of application and does not change if the tenacity changes.

Increasing tenacity

Tenacity can be increased with champion abilities, items, runes, and summoner spells, stacking either multiplicatively or additively depending on the combination of the effects.

Items

• Mercury's Treads
• Silvermere Dawn
• Sunfire Aegis ( Forgefire Crest)

Elixirs

• Elixir of Iron

Champion abilities

• Garen's Courage

Runes

• Legend: Tenacity
• Unflinching

Summoner Spells

• Cleanse

Game Modes

• Ultra Rapid Fire
• Ultimate Spellbook

Reducing Tenacity

Tenacity can be reduced to negative values, causing crowd control to last longer.

Champion Abilities

• Ornn's Bellows Breath and Call of the Forge God apply Brittle, which is a unique status effect that reduces tenacity by 30%.

Items

• Anathema's Chains reduces the Nemesis' tenacity by 20% while at maximum stacks of Vendetta. This stacks multiplicatively with Brittle for a total of -56% tenacity.

Monsters

• Rift Scuttler has -100% tenacity, doubling the duration of crowd control effects applied to her. This stacks additively with Brittle for a total of -130% tenacity.

Stacking

The tenacity stat is build up from sub-stats that internally are referred to as "modifiers". For the lack of naming scheme, the LoL Wiki simply refers to these as types, from A to E. Combination of effects in the same type will stack additively, while combination of multiple types will stack multiplicatively.

The math for the total tenacity looks like this:
1 - (1 - (A1 + A2 + ...))  ×  (1 - (B1 + B2 + ...))  ×  (1 - (C1 + C2 + ...))  ×  (1 - (D1 + D2 + ...))  ×  (1 - (E1 + E2 + ...))

	Source
Type A	Mercury's Treads Anathema's Chains (debuff) Silvermere Dawn (active).
Type B	Sunfire Aegis ( Forgefire Crest) Elixir of Iron Unflinching
Type C	Courage Brittle Rift Scuttler's negative tenacity Ultimate Spellbook's innate buff Ultra Rapid Fire's innate buff
Type D	Cleanse
Type E	Legend: Tenacity

Calculation (Example)

Say, your character has Mercury's Treads in their inventory and fully stacked Legend: Tenacity in their runes. A nearby enemy reduces your Tenacity via Anathema's Chains. Then your Tenacity adds up like this:

• Type A Tenacity modifiers = 30% + -20%
• Type E Tenacity modifier = 30%
• Final Tenacity = 1 - (1 - Type A Tenacity modifier)  ×  (1 - Type E Tenacity modifier)
  • = 1 - (1 - ( 0.3 + -0.2)) × (1 - 0.3)
  • = 1 - (0.9) × (0.7)
  • = 1 - 0.63 = 0.37 = 37%

Trivia

• Until patch V1.0.0.118, Tenacity was an unnamed effect unique to Mercury's Treads. That patch promoted the effect to a champion statistic and added three new items: Cloak and Dagger, Eleisa's Miracle and Moonflair Spellblade (all later removed). Tenacity from multiple sources did not stack, similar to Enhanced Movement. In Season Three there was an item overhaul, named item effects were introduced, and Tenacity was reverted to an item effect. In V3.01, all sources of crowd control reduction were changed to say "Tenacity" and Tenacity was reintroduced as a champion statistic.
• Until Season Three, Tenacity's in-game icon was the same as the icon used for Cho'Gath's Vorpal Spikes and Baron Nashor's passive. Between the introduction of season 3 changes and V3.01, it shared the same icon as the Tenacious mastery. As of V3.01, it no longer has an icon in the buff bar.
• Prior to the Preseason of 2021, a website news post was made that announced that Tenacity would reduce the duration of knockups. However, the change was confirmed to have been cancelled.
  • Predating the announcement, in the V4.01 April Fools' Day patch, the following change regarding tenacity was jokingly listed:
    • Knockups are now reduced by Tenacity and other forms of crowd control reduction.
• Prior to his VGU in patch V11.12, Dr. Mundo's Burning Agony granted himself 30% Tenacity which was additive with other "Champion Tenacity" buffs such as Brittle.
• Prior to V3.04, Singed's Insanity Potion granted himself 10 / 15 / 20% Tenacity.

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Last updated: June 24, 2021, patch V11.13

• The biggest amount of Tenacity you can obtain is 99.265% with Garen.
  • Courage
  • Mercury's Treads
  • Silvermere Dawn
  • Sunfire Aegis
  • Elixir of Iron
  • Unflinching
  • Cleanse
  • Legend: Tenacity

1 - ((1 - 0.6) × (1 - ( 0.3 + 0.4)) × (1 - ( 0.05 × 4 + 0.25 + 0.3)) × (1 - 0.65) × (1 - 0.3) = 

1 - (0.4 × 0.3 × 0.25 × 0.35 × 0.7) = 99.265%

• With this amount of tenacity, Nasus' Wither (longest crowd control in the game) would only last 0.03675 seconds. The minimum crowd control duration prevents this.
  • In comparison, Nasus' Wither would last 7.8 seconds if the target has no tenacity and is Brittled and affected by Anathema's Chains.
• Note that this amount of tenacity can only be achieved briefly with Courage wearing off almost immediately, and with Cleanse and Silvermere Dawn which grant a temporary buff.

Champion statistics