There's two diffrent Accuracy's. There is your Accuracy score which is just a number and there is your Chance To Hit which is a percentage.
  • Accuracy score is based on Agility and Survival.
  • This score is then modified by all of your equipment and skills.
  • Then this number is compared to the target's Evasion score (how they relate I'm not entirely sure).
  • The result from that is your Chance To Hit.

For example:

70 Accuracy from Agility and Survival.
-10% from equipment.
+40% from Weapon Skill.

70 x (100 – 10 + 40)%
= 70 x 130%
= 91 Accuracy

Hope this helps!