> but wouldn't you need 101 sides to get 0% and 100% for that?

There is no 0% in d100/d-percentile rolls. Every "how to interpret these dice" paragraph in games which use them will tell you to interpret 0-0 on 2d10 as 100, not 0. Or, hypothetically (but i don't recall having ever seen this), they'll have a stated range of 0 to 99 (inclusive). Either way, the numeric range spans precisely 100 digits.

▲

1313ed01 2 days ago | parent | next [-]

There are games that use a d100 with 0-99 range, and games that read a d10 as 0-9 for that matter. First that comes to mind is Ambush! from 1983 that did both those things (https://boardgamegeek.com/boardgame/1608/ambush).

Love that game, but it is a bit distracting that probabilities feel one-off. Rolling 5 or lower to hit is 60%, not 50%. And when rolling 2d10 the result is 0-18, not 2-20.

▲

PunchyHamster 2 days ago | parent | prev [-]

yeah but that means there is no 0% on the scale

▲

Karliss 2 days ago | parent [-]

The point of percentile dice isn't to generate a string between "0%" and "100%", it is to test if action with chance of x% success gets done or not. For every o value of x, there are x out of 100 values which are strictly less than x, or if you count 0 as 100 then there are x out of 100 values which are less than or equal to x. Either way you get x% percent chance for event to happen. If the dice had 101 sides, the probabilities would be x/101 which aren't nice round percents.

It even works correctly for 0% and 100% chance events. Assuming 0 is counted as 0 - For 0% there are 0 numbers less than 0 on dice so chance of throwing number less that is 0/100=0%. For 100% all 100 numbers are less than 100 so no matter what the result of throw is you will succeed.

▲

tialaramex 2 days ago | parent [-]

Not necessarily "done or not" because it's narratively unsatisfying to just "fail". Imagine you watch a heist movie and in the last 20 minutes the gang are like "Stealing the master key to make a copy was vital to our plan but we failed" and they disband and that's the end of the movie. Realistic but not satisfying and the dice are for a game, a fiction, so we can just eliminate that unsatisfying result.

Modern systems tend to come up with some more interesting consequences, so e.g. maybe success is the thing the player wanted to do succeeds as they expected, but failure shades from "Small snag" to "Technically it did work, but..." like from "The target's PA, Betty, noticed you take the key, so now you also need to bribe Betty" through "Our copy won't actually work, we're going to need to keep the original and hope the copy fools them for long enough"

Or maybe we have a timing adjustment, success means that you pilfer the key, duplicate it in five minutes like planned and slip it back, mild failure is it takes a half hour and everybody will need to improvise for those extra minutes, and bad failure is you'll need it all night, change your plans to accommodate that.

	▲	chuckadams 2 days ago \| parent [-]
		The usual RPG response to the failed critical skill check is that the party just slaughters everyone in the casino instead.