DM Entry: Minus 10 and Half It

I stumbled upon an easy formula that you can use to quickly determine the modifier for any ability score.

Ability Score minus 10, then divide by 2 (round down).

It works for all ability scores, those with positive and negative modifiers.

For example,

15 - 10 = 5.....then 5 divided by 2 = 2.5 (rounded down to 2)....so ability score 15 has a modifier of 2.

30 - 10 = 20....then 20 divided by 2 = 10...so ability score 30 has a modifier of 10.

18 - 10 = 8....then 8 divided by 2 = 4...so ability score 18 has a modifier of 4.

4 - 10 = -6....then -6 divided by 2 = -3...so ability score 4 has a modifier of -3.

1 - 10 = -9....then -9 divided by 2 = -4.5 (rounded down to -5...so ability score 1 has a modifier of -5.

So with this formula you can easily and quickly derive the ability score modifier for any ability score, without looking up charts. Even for numbers that are larger than what appears on the charts in the Player's Handbook.

Thor has a Strength score of 92.
92 - 10 = 82
82 divided by 2 = 41.
So Strength score of 98 has a modifier of 41.

I think this will make it easier to determine ability score modifiers on the fly for numbers that are unusual (like those not listed in the Player's Handbook chart).

So just remember:
Minus 10 and half it.