Confused at miss chance percentile rolls and concealment. [D&D 3.5]

[Star_In_a_Sky]

Hi all. :smallsmile:

Just confused about miss chance percentile rolls and concealment.

Specifically, I'm in a situation where I'm almost sure I have to beat a 20% miss chance. But I don't really know what I'm supposed to roll. I don't have any item or outside influence that can get past it; nothing that will make the concealment go away. Again, it's just that I really don't know what I'm expected to roll, or what a 'good' result is. I need to know for a story on this forum.

So, if it's not a normal 1d20 to beat the 20% concealment, what am I expected to roll? And what kind of result is good for me? Is a low number good at beating that 20% or a high number (like normal)?

Sorry for the simple question, but I couldn't find an answer on http://www.d20srd.org.

[unbeliever536]

For the future, questions like this are best asked in this (http://www.giantitp.com/forums/showthread.php?t=318591) thread.

What you do is roll two ten-sided dice. One generates the tens digit of the result; the other is the ones digit (you declare which is which before rolling, of course). If you buy a set of dice, it'll often include an extra ten-sided die marked for this purpose. Rolls are usually considered to be in the range 01-100, so you need a result strictly greater than 20 to hit in the case you described. Of course, for miss chances, you don't really need to use this system (called a d%), but it works well for big tables of treasure and such.

[Vaz]

If you have a miss chance, roll for each attack that's going to hit. It's not a modifier, it's an additional roll. Choose the dice range (say on a d20, you might say that 1-4 is a 20% miss chance) that is equal to the miss chance; and roll it; if you get a number within that range (say you roll a 3), that attack has missed.

If you roll outside of that range, then your attack continues.

I'll have to double check what multiple miss chances refers to, but I think that each miss chance (say you have a 20%, and a 10% miss chance) you get another dice. If either one is within their range (say the 10% range, you might get higher, but the 20% roll you make), the attack missed.

As you can see, the more miss chances you have, the better it is. Some explicitly do NOT stack, however, so be careful. On the other hand, for simplicitity and speed, just take the highest miss chance.

[Star_In_a_Sky]

For the future, questions like this are best asked in this (http://www.giantitp.com/forums/showthread.php?t=318591) thread.

Sorry, now I know. :smallcool:


What you do is roll two ten-sided dice. One generates the tens digit of the result; the other is the ones digit (you declare which is which before rolling, of course). If you buy a set of dice, it'll often include an extra ten-sided die marked for this purpose. Rolls are usually considered to be in the range 01-100, so you need a result strictly greater than 20 to hit in the case you described. Of course, for miss chances, you don't really need to use this system (called a d%), but it works well for big tables of treasure and such.


If you have a miss chance, roll for each attack that's going to hit. It's not a modifier, it's an additional roll. Choose the dice range (say on a d20, you might say that 1-4 is a 20% miss chance) that is equal to the miss chance; and roll it; if you get a number within that range (say you roll a 3), that attack has missed.

If you roll outside of that range, then your attack continues.

I'll have to double check what multiple miss chances refers to, but I think that each miss chance (say you have a 20%, and a 10% miss chance) you get another dice. If either one is within their range (say the 10% range, you might get higher, but the 20% roll you make), the attack missed.

As you can see, the more miss chances you have, the better it is. Some explicitly do NOT stack, however, so be careful. On the other hand, for simplicitity and speed, just take the highest miss chance.

So roll either a 1d100 or a 1d20, low results bad for me (because in this case, they represent that 20% concealment), plus more information regarding multiple miss chances and treasure tables if I ever get stuck with expanded versions of this problem. :smallbiggrin:

You guys are great. Thank you.

[The Insaniac]

One thing to keep in mind is that multiple miss chances of the same type (typically concealment) don't stack. You'd only need to roll against the largest chance.

[Chronos]

You can do it any way that gives you the right probability, so long as you're clear on what you're doing. If, for instance, it's a 50% miss chance, you could flip a coin and say "Heads is a hit" before you do it. Or you could roll a die and say "high rolls hit", or "even hits". All of these are fine, because they're all a 50% chance.

A 20% chance is a little more limited, since you can't easily generate that with most dice. You're going to end up needing to use either a d10 or a d20. The easiest would be to roll a d10, and pick two numbers that will count as a miss. You could do this with "1 or 2 is a miss", but you could also say "9 or 0 is a miss", or even "3 or 7 is a miss". Again, of course, you need to say what you're counting before you roll.