# How to calculate score from XP

My mathematical skills seem to have abandoned me (temporarily I hope...).

How do I calculate what the score for a skill or art is, given the XP. I'm trying to make some autocalculations for my character sheets, and besides making a long list I simply cont get my head around it.

Does anyone have a nice formula fit for programming or a spread sheet?

skill levels n -->xp needed

n + (n-1)* n/2 (for arts)

5*(n+(n-1)*n/2) for abilities

If you have x experience points in an Art, the score in the Art is (SQRT(8x+1)-1)/2, rounded down.
If you have y experience points in an Ability, the score in the Ability is (SQRT(8y/5+1)-1)/2, rounded down.

Thanks. I knew how to calculate the other way but just couldn't get my head around this direction

It's simply the same formula but using the variable as the unknown value
I had a hard time too to figure it out but when i started to do maths with the initial formula, it just came back.

Yep.

But it's been so long since Algebra that I actually had to look up the formula for the quadratic equation. My son would laugh at my face knowing that I can't even do basic maths without support literature any more

I'll just go and hide in a corner while using the formula in my little program

Yeah this is correct. I used the quadratic formula for this too.

I would also point out that, for practical purposes, the best way to compute it (whether on a computer or by hand) is just a table look up After all, you are never going to see scores above 100 ...

n*(n+1)/2 is simpler. {18 -> 9*19 = 171 ; 19 -> 19 * 10 = 190}

Does anyone knows the formula to calculate the final score of an attribute from the aging points allocated to it?

Replace (x) with (x-a), where (a) is the number of aging points. Also, since you can't use the wrong (x) when buying the characteristic and since aging points themselves effectively round down, you'll want to round up. So Gerg's formula becomes:

If you have x points and a aging points in a Characteristic, the score in the Characteristic is (SQRT(8x-8a+1)-1)/2, rounded up.

Edit: You can change this to (SQRT(4[i]n/i-8a+1)-1)/2, rounded up, where n is the original number.

However, this may break down at zero. I'll have to double-check the rules on the negatives and zero.

Chris

Thank you very much! It works although, as you mention, breaks for negative numbers

If you're doing it in MSExcel, programming it yourself, or something similarly versatile, you could add a conditional statement to check for the zero-point, subtract to find the remaining negative points, and then apply the same formula in a positive sense, tossing a negative on it in the end. If that's not clear, I can write something more comprehensive for you later. If so, do let me know what you're using.

Chris

I am using Open Office Writer and the formula I included is:

IF((4B1(B1+1))<8B2;(-1)ROUNDUP((SQRT(ABS(4B1(B1+1)-8B2)+1)-1)/2);ROUNDUP((SQRT(4B1*(B1+1)-8*B2+1)-1)/2))

Now it works, even for negative! I have an spreadsheet to keep track of my character and the only piece I felt was missing was the aging. Now I am ready to adventure in the lands of magic . Thank you very much indeed!

A roleplaying-math-hint:
wolframalpha.com/input/?i=y% ... olve+for+x

Very useful if those math lessons were eons ago... :mrgreen: