How to read a d100

[Felhammer]

Across my many years of gaming, I have seen many people interpret a d100 roll differently. I was curious to see what the consensus was on the internet, if there is any. Obviously this is a discussion about the traditional hundreds d10 and the normal d10 (not the d100 golf ball).

When you roll the following, what do you interpret the dice as:

A: 0 on the unit die and 00 on the tens die.
B: 1 on the unit die and 00 on the tens die.
C: 0 on the unit die and 40 on the tens die.


I have seen people say the A) is 100 or 10. B) is 100 or 1. C) is 40 or 50.

Like I said, I'm just trying to see what the internet says is the most common answer.

[hamishspence]

I tend to call it a "tens dice" and a "units dice".

Since there's no such thing as "rolling a 0 on d100"- the lowest you're supposed to be able to roll is 1 and the highest 100- then it follows that 0 on both dice corresponds to 100, not 0.

But this only applies to double zeroes.

40 on the tens dice, 0 on the units dice, would be 40.
00 on then tens dice, 1 on the units dice, would be 1

[Glimbur]

When you roll the following, what do you interpret the dice as:

A: 0 on the tens die and 00 on the hundreds die.

I read that as 100.

B: 1 on the tens die and 00 on the hundreds die.

I call that 10.

C: 0 on the tens die and 40 on the hundreds die.

That's a 40.

[jaybird]

C: 0 on the tens die and 40 on the hundreds die.


I have seen people say the A) is 100 or 10. B) is 100 or 1. C) is 40 or 50.

Huh? 0/4 works out to 4, not 40. 0/0 indicated 100, 0/anything else indicates single digit that (so 0/1 would be 1).

[Sidmen]

I'll admit, I'm not sure how this causes confusion.

When you roll a die that says 40 on it, then another that says 7, how can anyone not read that as 47.

The only one I can see anyone reading with confusion is when they roll 00 and 0; which is 100 (because no other die roll can be 100, and 000 isn't valid).

[Felhammer]

I tend to call it a "tens dice" and a "units dice".

Since there's no such thing as "rolling a 0 on d100"- the lowest you're supposed to be able to roll is 1 and the highest 100- then it follows that 0 on both dice corresponds to 100, not 0.

But this only applies to double zeroes.

40 on the tens dice, 0 on the units dice, would be 40.
00 on then tens dice, 1 on the units dice, would be 1

Oops, yes I meant tens and units dice.

If you cannot roll a 0, then how does a 40 and a 0 = 40? Should it not be 50? (just playing devil's advocate here).

I read that as 100.
I call that 10.
That's a 40.

Interesting, thanks for the swift reply.

I'll admit, I'm not sure how this causes confusion.

When you roll a die that says 40 on it, then another that says 7, how can anyone not read that as 47.

The only one I can see anyone reading with confusion is when they roll 00 and 0; which is 100 (because no other die roll can be 100, and 000 isn't valid).

Hence why I didn't ask about 47.

Technically speaking a 90 and a 0 could equal 100, if you assume the 0 is a 10 and not a 0. By the same token, how does a 00 and a 0 = 100, when it could just as easily equal 10.

[toapat]

I'll admit, I'm not sure how this causes confusion.

When you roll a die that says 40 on it, then another that says 7, how can anyone not read that as 47.

The only one I can see anyone reading with confusion is when they roll 00 and 0; which is 100 (because no other die roll can be 100, and 000 isn't valid).

D%'s 0/00 Roll is actually a dependant result.

D20 typically assumes that it is a roll of 0, not 100, but the bleed out rules use the D% dice in their inverse roll. a roll of 0/00 is a 100% chance to stabilize.

[TuggyNE]

A: 0 on the unit die and 00 on the tens die.
B: 1 on the unit die and 00 on the tens die.
C: 0 on the unit die and 40 on the tens die.

I don't know about common, but the correct answers are (as mentioned) A: (1)00; B: 01; C: 40.

It might help if they were presented (and rolled) as tens and then ones; that's more natural for what is essentially a positional notation reading exercise. A is a bit tricky because most people don't do much with integer over-/under-flow, so realizing that the basic answer of 00 is then treated as 100 is non-trivial. The only way to get B wrong is reading in the wrong order, I think. C is only difficult if you don't understand the basis of positional notation (i.e., the radix itself is never expressible in a single digit — in base ten, ten is two digits, or 10, and a given column goes from 0 to 9, not 1 to 10).

I've learned not to be too surprised at what people do or don't understand about fundamental math, though, especially because fundamentals are often ignored in practice in favor of loose approximations.

[jindra34]

If you cannot roll a 0, then how does a 40 and a 0 = 40? Should it not be 50? (just playing devil's advocate here).

Because your rolling the digits to be placed in those slots not actual numbers. So from 1(01)-100 each combination of a tens digit and a units digit appears once. And 00 happens to appear in 100, and 40 has a 4 in the tens digit and a 0 in the units digit. Does that help?

[Felhammer]

I don't know about common, but the correct answers are (as mentioned) A: (1)00; B: 01; C: 40.

It might help if they were presented (and rolled) as tens and then ones; that's more natural for what is essentially a positional notation reading exercise. A is a bit tricky because most people don't do much with integer over-/under-flow, so realizing that the basic answer of 00 is then treated as 100 is non-trivial. The only way to get B wrong is reading in the wrong order, I think. C is only difficult if you don't understand the basis of positional notation (i.e., the radix itself is never expressible in a single digit — in base ten, ten is two digits, or 10, and a given column goes from 0 to 9, not 1 to 10).

I've learned not to be too surprised at what people do or don't understand about fundamental math, though, especially because fundamentals are often ignored in practice in favor of loose approximations.

That is a great explanation.

I've always assumed rolling a d100 worked the way you described, until I encountered other people who do it differently.

One of the players in my group actually interprets his d100 rolls in such a manner as to answer the questions from the first post as 10, 1 and 50. He does this because the first set of dice he ever owned were different than the standard dice everyone uses. The regular d10 actually had a 10 listed on it (rather than a 0), so he's always assumed you simply add the dice together, rather than using positional notation.

He's always been an oddity, until I started gaming with people in open playgroups (like D&D Encounters) and met other people who interpret the dice differently (and to be honest, they do it in very bizarre and inconsistent manner).

It's always surprised me that people don't pick up on how to roll the d100 in the standard way. However, I figured before I go around mentioning the fact that they are rolling their dice incorrectly, I should check and see if I was actually the oddity and they the norm.

[Malak'ai]

They way I was taught when I first started playing MERP/RoleMaster was to ignore the "0" and the "00" on the Unit's and Ten's dice, which would only give nine valid outcomes for each (1-9 and 10-90). The only time to even worry about them was when you rolled "00,0" giving you 100.

[Frozen_Feet]

I don't use the 00 die at all. I use two differently coloured d10s, treating two 0s as either 100 or 0 based on the game.

[toapat]

I don't use the 00 die at all. I use two differently coloured d10s, treating two 0s as either 100 or 0 based on the game.

actually 00/0 if you are going from 1-100 is 10, D20 treats it as 0

[huttj509]

actually 00/0 if you are going from 1-100 is 10, D20 treats it as 0

If 00/0 is 10, 10/0 must be 20 in order to remain consistent.

I've never seen a table in the d20 system labeled from 0 to 99, always 1-100, so I'm not sure what you mean by "D20 treats it as 0."

Dice are die a and die b:

System A: Each die is numbered 0-9. Result is read as (a*10)+b=result. A result of 00 is read as 100.

System B: Each die is numbered 1-10. Result is read as (a*10)+b=result, with results above 100 wrapping round to the numbers 1-9.

[toapat]

If 00/0 is 10, 10/0 must be 20 in order to remain consistent.

I've never seen a table in the d20 system labeled from 0 to 99, always 1-100, so I'm not sure what you mean by "D20 treats it as 0."

Dice are die a and die b:

System A: Each die is numbered 0-9. Result is read as (a*10)+b=result. A result of 00 is read as 100.

System B: Each die is numbered 1-10. Result is read as (a*10)+b=result, with results above 100 wrapping round to the numbers 1-9.

every table ive seen is 0-99 for RNG in DnD.

for random number generation, the D10's 0 is 0, for damage, when you are forced to use the d100 (which i havent seen in pen and paper) the D10 is 10. this means that a roll of 90/0 for RNG is 90, while for damage, a roll of 90/0 is 100.

This is the standard in dungeons and dragons, and it is how you are supposed to read the dice

[tyckspoon]

every table ive seen is 0-99 for RNG in DnD.

for random number generation, the D10's 0 is 0, for damage, when you are forced to use the d100 (which i havent seen in pen and paper) the D10 is 10. this means that a roll of 90/0 for RNG is 90, while for damage, a roll of 90/0 is 100.

This is the standard in dungeons and dragons, and it is how you are supposed to read the dice

The Confusion spell, Reincarnate, the random treasure tables, weather tables.. they're all 1-100. Could I ask what version of DnD you're thinking about? It doesn't appear to be 3.5... and I'd have to think a bit to figure it out, but I'm pretty sure your way of reading the dice means there's at least one number it's impossible to roll and several ways to roll others, which would suggest it's incorrect on a roll that's supposed to have an even chance of the entire 1-100 range.

[Jeraa]

d%: Percentile dice work a little differently. You generate a number between 1 and 100 by rolling two different-colored tensided dice. One color (designated before you roll) is the tens digit. The other is the ones digit. A roll of 7 and 1, for example, give you a result of 71. Two 0s represents 100. Some percentile show the tens digit in tens (00, 10, 20, etc.) and the ones digit in ones (0, 1, 2, etc.). In this case, a roll of 70 and 1 is 71, and 00 and 0 is 100.

From the 3.5 PHB, page 5. In D&D, 00/0 is always 100. Never 0.

The Confusion spell, Reincarnate, the random treasure tables, weather tables.. they're all 1-100. Could I ask what version of DnD you're thinking about? It doesn't appear to be 3.5...

Its not 1st or 2nd edition AD&D either*. Both editions had the d100 results going from 01 to 00. 00 being how they wrote 100. You know it meant 100 and not 0, as it was always at the bottom of the charts, after the 90's (like 91-00), and never at the top (like 00-09).

*Unless there was some obscure table I missed when I looked just now.

[toapat]

The Confusion spell, Reincarnate, the random treasure tables, weather tables.. they're all 1-100. Could I ask what version of DnD you're thinking about? It doesn't appear to be 3.5... and I'd have to think a bit to figure it out, but I'm pretty sure your way of reading the dice means there's at least one number it's impossible to roll and several ways to roll others, which would suggest it's incorrect on a roll that's supposed to have an even chance of the entire 1-100 range.

I seem to be thinking of an extended list for Reincarnation, which i cant find. also DDO/bleeding out which is also bull****, because when they give you a +10 bonus after lvl 2 to the roll (IE, can never roll the 0-9 needed to stabilize without Diehard)

And no. Neither way of reading the die yields a duplicate result. in one, 00/0 yields 10 while 10/0 yields 20, on the other (IE, you are reading both Dice as normal rolls), this results in 00/0 yielding 0, while 10/0 yields 10.

Getting a duplicate roll is actually impossible no matter how you read both dice. It is just that reading both dice straight makes seems more nonsensical

[Mando Knight]

every table ive seen is 0-99 for RNG in DnD.

for random number generation, the D10's 0 is 0, for damage, when you are forced to use the d100 (which i havent seen in pen and paper) the D10 is 10. this means that a roll of 90/0 for RNG is 90, while for damage, a roll of 90/0 is 100.

This is the standard in dungeons and dragons, and it is how you are supposed to read the dice

From the 3.5 PHB, page 5. In D&D, 00/0 is always 100. Never 0.



Its not 1st or 2nd edition AD&D either*. Both editions had the d100 results going from 01 to 00. 00 being how they wrote 100. You know it meant 100 and not 0, as it was always at the bottom of the charts, after the 90's (like 91-00), and never at the top (like 00-09).

*Unless there was some obscure table I missed when I looked just now.

Other examples supporting 00/0 as 100 are all of 3.5's random tables (numbered 01-100), such as Reincarnate or random magic item distribution, randomized environments, and so forth. (At least in core, the random tables 4e has are generally d20 based rather than d%)

[TuggyNE]

One of the players in my group actually interpret his dice together in such a manner as to answer the questions from the first post as 10, 1 and 50. He does this because the first set of dice he ever owned were different than the standard dice everyone uses. The regular d10 actually had a 10 listed on it (rather than a 0), so he's always assumed you simply add the dice together, rather than using positional notation.

Yeah, marking a d10 with 1 through 10 seems like a handy thing to do, but it's misleading for d100 purposes because you're actually using two digits, not just one. (Similarly, d12s and d20s are a little odd, though not as bad because no one would use them for anything but their primary purpose.)

It might help to make a chart or something, comparing the results between interpretations.

*Ponders whether to include this in an edit*

They way I was taught when I first started playing MERP/RoleMaster was to ignore the "0" and the "00" on the Unit's and Ten's dice, which would only give nine valid outcomes for each (1-9 and 10-90). The only time to even worry about them was when you rolled "00,0" giving you 100.

That's ... kind of confusing. It's a base 10 system, not a base 9 system; there are 10 valid digits in any given position (starting with 0, and wrapping around after 9).

also DDO/bleeding out which is also bull****, because when they give you a +10 bonus after lvl 2 to the roll (IE, can never roll the 0-9 needed to stabilize without Diehard)

I've never seen this in DDO, and I can distinctly remember stabilizing after level 2 by random chance on at least one occasion.

Getting a duplicate roll is actually impossible no matter how you read both dice. It is just that reading both dice straight makes seems more nonsensical

As long as you're consistent, this is true. However, several techniques encourage inconsistency, or make it easy to confuse the result, or both, as has already been demonstrated.

[toapat]

I've never seen this in DDO, and I can distinctly remember stabilizing after level 2 by random chance on at least one occasion.

As long as you're consistent, this is true. However, several techniques encourage inconsistency, or make it easy to confuse the result, or both, as has already been demonstrated.

ive done it once too, I had the Threnal Arnessan cloak though, and that stabilized me. typically you just either get blown appart or CDG'd

So long as everyone is clear on the current way the D% set is being read, its fine

buying the Dgolfball is better though, because you CANT read that thing wrong.

[tyckspoon]

buying the Dgolfball is better though, because you CANT read that thing wrong.

I've had them before. They're quite easy to misread, IME, due to how close together the facets are; it's not very easy to pick out which one is actually on top quickly.

[huttj509]

That's ... kind of confusing. It's a base 10 system, not a base 9 system; there are 10 valid digits in any given position (starting with 0, and wrapping around after 9).

I think what Malak'ai is talking about is (format (a,b) means (tens die, ones die)):

(0,0) = special case, 100.
(0,7) = ignore the tens die, just 7.
(8,0) = ignore the ones die, just 80 (tens die times 10).

So it's the same as what most of us in this thread do, but the 'ignore zeroes' can distract from realizing that it's the same.

But yeah, the 1-10 method isn't wrong, just different from what many of us are used to:

(10,10) = 110, drop the hundreds place for a result of 10.
(10,7) = 107 = result of 7
(8,10) = 80 + 10 = 90.
(9,10) = 100 (90 + 10).

I can definitely see that method coming easier to some people, since we normally read the 0 as 10 when rolling a single d10.

Anyone trying to switch between methods, however, (say, if they're used to one but being pressured to use the other) is gonna make loads of mistakes for a bit. As long as someone's consistent, those methods are both valid. Though it's useful if everyone at the table uses the same method, otherwise you get "woo, 100!" "But you rolled a 90."

[Jack of Spades]

buying the Dgolfball is better though, because you CANT read that thing wrong.

Eh, the golfball is a bit gimmicky. Overpriced (usually, for dice), rather hard to read in the first place (accuracy aside), only fulfills a single purpose which is almost as rare as a d12 roll in 3.x, and is the only "die" that requires a 100% flat surface to be usable/random because of how small the faces are.

[Malak'ai]

That's ... kind of confusing. It's a base 10 system, not a base 9 system; there are 10 valid digits in any given position (starting with 0, and wrapping around after 9).

I think what Malak'ai is talking about is (format (a,b) means (tens die, ones die)):

(0,0) = special case, 100.
(0,7) = ignore the tens die, just 7.
(8,0) = ignore the ones die, just 80 (tens die times 10).

So it's the same as what most of us in this thread do, but the 'ignore zeroes' can distract from realizing that it's the same.

But yeah, the 1-10 method isn't wrong, just different from what many of us are used to:

(10,10) = 110, drop the hundreds place for a result of 10.
(10,7) = 107 = result of 7
(8,10) = 80 + 10 = 90.
(9,10) = 100 (90 + 10).

I can definitely see that method coming easier to some people, since we normally read the 0 as 10 when rolling a single d10.

Anyone trying to switch between methods, however, (say, if they're used to one but being pressured to use the other) is gonna make loads of mistakes for a bit. As long as someone's consistent, those methods are both valid. Though it's useful if everyone at the table uses the same method, otherwise you get "woo, 100!" "But you rolled a 90."

The "ignore the "00" or "0"" is actually easy to understand when being told how to use a d100 for the first time as with a d100 rolling 10,0 gives a result of 10 (1 ten, 0 units) so you just ignore the "0" and read off the tens die. A roll of 00,9 gives a result of 9 (0 tens, 9 units) so in this case you ignore the "00" and read off the units die.

I know it's a bit of a round about way to explain how to read a d100 roll but when explained in person, the way I was, it became really easy to understand.

[Ravens_cry]

You can't roll a 0 on any other die commonly used in gaming (d2, d3, d4, d6, d8 d10, d12, d20), as well as more esoteric shapes like d30 and d14, why would you want to for a d100?

[lesser_minion]

By default, a zero on a d10 is read as zero, and the same applies to case A from the OP.

Treating zero as ten or one hundred is a game mechanic, not an inherent part of the conventions for reading dice. It usually applies, but it varies from game to game.

You'll note that d10s numbered from 0 to 9 often do treat the 0 as zero -- opposite faces of the die sum to nine rather than eleven.

[Jay R]

It's quite simple, once you realize that there is one case that requires an exception. Have you ever been in a car when the odometer runs out of digits? It suddenly rolls over from 99999 to 00000. It's clear that the car has gone 100,000 miles (or kilometers), not zero.

Dice are the same. To roll a 1-100, you need to roll two ten-sided dice, to generate two digits. But one time in 100, you need a 3-digit number.You always read the dice the same. In the one exceptional case, you do something else in addition.

Every number from 1 to 100 has a unique two-digit set in the tens and units places. The number on the tens die is the tens digit - always. The number on the unit digit is the units - always.

In one case in 100 (when you roll 00 and 0), you need a hundreds digit. Use 1, and the number is 100.

[toapat]

The "ignore the "00" or "0"" is actually easy to understand when being told how to use a d100 for the first time as with a d100 rolling 10,0 gives a result of 10 (1 ten, 0 units) so you just ignore the "0" and read off the tens die. A roll of 00,9 gives a result of 9 (0 tens, 9 units) so in this case you ignore the "00" and read off the units die.

I know it's a bit of a round about way to explain how to read a d100 roll but when explained in person, the way I was, it became really easy to understand.

the only problem there is there is an arbitrary 100 where a 0 should be

@ someone else: interesting catch finding that the D10 is carved wrong

[The Dark Fiddler]

When you roll the following, what do you interpret the dice as:

A: 0 on the unit die and 00 on the tens die.
B: 1 on the unit die and 00 on the tens die.
C: 0 on the unit die and 40 on the tens die.

It seems I do it differently from everybody else, maybe because I tend to use 2d10 rather than a d% and a d10? Regardless, I'd read them as:

• A) 10
• B)1
• C)50

This is because 0 on a d10 is actually a 10, so A would be (00+10), B would be (00+1), and C would be (40+10).