AR and DR Guide, lifed from granadocafe

What does AR and DR refers to?
AR refers to Attack Rating, DR refers to Defense Rating.

How do you calculate how much ar and dr a character/monster has?
(Character Level/4) + (Equipment level/4) = AR or DR
All values are rounded down (just remove any decimals you get when you divide the levels by 4. To calculate monster AR n DR, you can simply take the monster's level divided by 2 and round down the value if there's decimal place. The formula is the same for monster, just that monster equipment level = monster level whereas a character varies. This AR DR calculation doesn't work for boss and mini boss.

Below is a AR DR chart for easy reference.

How does AR and DR work?
(ar - dr - 3) * 25% = damage boost
For e.g if your target has 10 dr, you will need 14 ar to get a 25% damage boost on him. If you have a 20 ar, you will get 175% damageboost on him. Note the damage boost is capped at 200%.

What if i got negative values from the calculation?
For every value below -1, you get a 10% damage penalty and 10% accuracy reduction. For e.g a 11 ar against a 12 dr target (11 - 12 = -1), you get 0% damage penalty and accuracy. whereas 11 ar against 13 dr target (11 - 13 = -2), you get 10% damage penalty and 10% accuracy reduction. And for 11 against 14 dr target, you get 20% damage penalty and accuracy reduction.

Credits to OpelxFrost for his generous offer of his GE Data guide