Formulas for D&D

[thol]

Does anyone have a link to a listing of the fomulas used for calculating things like ability score bonus, saves, etc.?

If there is no link that anyone knows of, can someone post them quick if they know them. I could figure them all out but if someone has them handy it would save me some time.

 

[dcollins]

On my website, I have a document called "Math Formulas for D&D". Look about 6 items down on this page: http://superdan.net.home.comcast.net/dnd3.html

 

[thol]

Thanks a bunch! Saves me a lot of time!

I can always count on ENWorld.

 

[thol]

Something you might want to fix on your document.

The formula for ability modifiers is off just a little. You end up with 3 ability mods of 0.

Looks like you need to do:

modifier = (ability / 2.1) - 5

and round to the nearest whole number

 

[Pinotage]

3 ability modifiers of 0?

Ability/2 -5 is the official formula. Can you give an example of those 3 which give 0. My calculations only give 2, for 10 and 11. Remember in D&D math you always round down.

Pinotage

 

[dcollins]

The formula for ability modifiers is off just a little. You end up with 3 ability mods of 0. Looks like you need to do: modifier = (ability / 2.1) - 5... and round to the nearest whole number

Let me guess what your problem really is: you're implementing this in a computer language, and unfortunately when you truncate a negative number, the result is effectively rounding up. (For example: 9/2 - 5 = -0.5 -> truncates to 0.)

EDIT: So make sure you do the truncation before you do the subtraction.

 

[Henry]

Looks like you need to do:

modifier = (ability / 2.1) - 5

and round to the nearest whole number

Not sure what you mean by that; it should be

modifier = INT(ability / 2) - 5, which is valid for ability scores from 1 on up.

 

[thol]

I was forgetting about INT.

In Excel, if you do Ability/2 -5 and Rounddown you end up with this string of mods for 1 to 20:

-4 -4 -3 -3 -2 -2 -1 -1 0 0 0 1 1 2 2 3 3 4 4 5

If you just Round, you end up with:

-5 -4 -4 -3 -3 -2 -2 -1 -1 0 1 1 2 2 3 3 4 4 5 5

That's why I was confused. I shouldn't try to do math before noon.

 

[thol]

Are there any formulas for the Spell Charts? They seem pretty wacky, especially the Sorcerer Spells Known table.

 

[Darkness]

In Excel, if you do Ability/2 -5 and Rounddown you end up with this string of mods for 1 to 20:

-4 -4 -3 -3 -2 -2 -1 -1 0 0 0 1 1 2 2 3 3 4 4 5

If you just Round, you end up with:

-5 -4 -4 -3 -3 -2 -2 -1 -1 0 1 1 2 2 3 3 4 4 5 5

Yep. In my chargen spreadsheet, I solved it by having Excel use an IF function first that leads to two slightly different formulas (one for >11, one for <11).