## Tuesday, June 8, 2021

### Precalculated XP totals

So here's a nifty thing! I've noticed in recent weeks that it's kind of annoying to calculate XP adjustments (you know, those +5% and +10% bonuses for having a high prime requisite ability score) at the end of every adventure. Not such a bother that I'd want to do away with the adjustments, but mildly annoying nevertheless. So I decided to tabulate separate XP charts for all possible XP adjustments! All it took was a little spreadsheet magic, and voila

Master XP Tables

I've created tables for every class that I allow in Dungeons & Dragons, Advanced Dungeons & Dragons, and Engines & Empires. As I expand my campaigns into other genres, I'll doubtless add pages to the document (since I know I'll be playing Raiders! of the Lost Artifacts, Freebooters, and White•Star eventually too)!

Since the D&D and AD&D pages do incorporate my house rules, I don't know how directly useful the document will be to anyone else, but at least it serves as a simple model for how to create one's own XP calculating tool. Just a bit of Excel formula, a bit of formatting, and some copy–paste action, that's all there is to it.

Yes sir, the fun never stops around here! ∎

#### 2 comments:

1. Couldn't you just reduce the amount required to advance by the same 5 or 10 percent?

1. That would be simpler, but also mathematically incorrect, as can be demonstrated by a bit of basic algebra.

If we let X equal the amount of XP earned and A equal the adjustment (bonus or penalty), we see that a typical XP award is calculated like this:

X + (X * A) = final award

where A can take values of −0.2, −0.1, 0.05, or 0.1

Factoring out the X gives us

X (1 + A) = final award

Which means that if we want to go in the other direction and instead of calculating the final award from the initial award (X) and the adjustment (A), we start with the final amount (i.e. the value we want to amass on the XP progression tables), we get

X = (final award)/(1 + A)

Where X is now the number we're looking for, the new XP table entry (and "final award" is given, as it's the old XP table entry). The equation's last term, meanwhile, (1 + A), can have values of 0.8, 0.9, 1.05, and 1.1, so calculating X is just a matter of dividing all the values on the book XP tables by those four factors. Easy peasy pi!