Sometimes a game tells you to use a "percentile dice" or a d100.
That can be confusing if you're not used to it, so here's how it's done.
Novelty die notwithstanding, there's no such thing as a d100.
Instead, you use any one of four methods:
* Two ten-sided dice (d10) rolled in succession
* Two different colours of ten-sided dice (d10) rolled together
* A percentile die and a d10
* Any other way you know to get a random number between 0 and 99
## Two ten-sided dice
You've gone out and bought exactly one dice set, and so you've got exactly one ten-sided die.
1. Roll your d10 once. This is the _tens_ place.
2. Roll your d10 again. This is the _ones_ place.
3. Picture the two numbers you just rolled, side by side, to form a single digit.
For example, suppose you rolled an 8 and then a 2.
You've rolled 82.
If you rolled a 1 and then a 9, then you've rolled 19.
If you rolled a 0 and a 1, then you've rolled a 1.
Here's the weird one: When you roll a 0 and a 0, you have rolled a 100.
## Two d10s in different colours
If you've got two d10s, each a different colour, then you can use one as the _tens_ die and the other as the _ones_ die.
Declare which is which _before_ you roll.
Personally, I have a green die that serves as my _tens_ die, and a black die for _ones_.
1. Roll both dice.
2. Assemble a number from your roll result, based on which colour represents _tens_ and _ones_.
For example, suppose you roll a 7 and 5.
You've rolled 75.
If you roll a 0 and 2, then you've rolled 2.
If you roll a 1 and 0, then you've rolled 10.
Here's the weird one: When you roll a 0 and a 0, you have rolled a 100.
## A percentile die and a d10
You can buy a special "percentile" die from your friendly local game store.
Instead of single digits, it's got double digits on it.
It's a lot like using a different colour die as your _tens_ die, except instead of a different colour it's just got more numbers on it.
1. Roll both dice.
2. Combine the percentile die with the d10 result.
For example, suppose you roll a 30 and a 3.
You've rolled 33.
If you roll a 00 and then a 3, then you've rolled 3.
If you roll a 10 and a 0, then you've rolled 10.
That's tricky, because it looks like 100, but it's not.
It's one _ten_ with zero _one_ added on.
So how do you get 100?
When you roll a 00 and a 0, you have rolled a 100.
If it helps, consider that the only time it's possible to get 100% of anything on percentile dice is when all digits are "0".
When you roll three 0s, you have the only 100% possible, at least visually, on those dice.
## High and low
Whether a roll of the highest value (000) is good, or whether you actually want a low roll (001) depends entirely on the game you're playing.
Games like **Call of Cthulhu** and **Stalking the Night Fantastic** reward low rolls (because you're aiming for a number within your range of skill), while other games reward high results because they represent a high likelihood of something occuring.
Regardless of the implications, though, you now know how to roll a d100.
