A critical strike in Elder Scrolls Online is when an ability, attack or healing does 50% more damage compared to normal. The chance for this to occur is called your critical strike rating or critical strike chance. All characters have a base critical strike rating of 10% which means that all characters have at least a 10% chance to cause a critical strike every time they damage or heal.
Spell Critical effects all abilities which use Magicka.
Weapon Critical effects all abilities which use Stamina.
Critical Strike Rating
You might notice that some item sets increase your critical strike rating with a flat number, not a percentage amount. This is due to internal workings of scaling critical strike chance up to higher Levels of items – previously all sets granted a flat percentage regardless of your Level. It’s difficult to convert the flat number to a percentage because it varies based on your Level.
The formula to work out the flat amount required for 100% critical is 2 * (Level) * (100 + Level).
This means that at Level 50 the flat number required for 100% critical is 15,000. This then tells us that 1,500 is the flat amount required for an extra 10% critical chance at Level 50. It also means that half of that, so 750, is required for an extra 5% critical chance at Level 50.
Increase Critical Chance
You can increase your critical strike rating and there is no limit on how much critical chance a character can have.