[RPG] Why does a d10 count from 0 to 9

dice

I have recently purchased (in Poland, if that matters) a set of dice, from d6 to d20.
I'm a complete newbie (if not ignorant) to RPG in general, dice, and this sort of technical stuff in practical, mainly because I was playing RPG very little in my life. But, since:

  • d6 allows to pick any number between 1-6 ("counts" to 6),
  • d8 allows to pick a number in 1-8 range,
  • d12 gives a number between 1 and 12,
  • d20 goes in 1-20 range, then…

…how it is possible, that d10 allows me to pick any number between… 0-9?

Did I just buy some weird dice or am I missing something obvious? As I said, I haven't been playing RPG or board games in general too much, but I have never seen or even heard of any dice that allows to pick zero.

Best Answer

There are 10-sided dice numbered 1-10. You should be able to find some easily if you search. But it's extremely common, especially among wargamers, to use 0-9.

There's a simple reason for this: Percentages.

Many systems use a percentile chance of something happening. By rolling two dice labelled 0-9, in different colours with one die chosen as the tens digit, you get a number from 0-99 - a percentage chance (often, but not always, counting 00 as 100).

This is much less readable if your dice are labelled 1-10, because you have to treat the 10 as 0 on both dice.