It also depends on how many more successes you need. If you're off by just a few, and you have a lot of failed dice, rerolling is better regardless of your Edge score. If you're off by a lot, or if most of the dice are successes and you're still down, adding your Edge is often the better move.

Here is me going through the math (roughly). I only used one set of exploding sixes (to simplify the math), so it is a rough estimate.

This all assumes that you are deciding before you even roll (enabling you to use rule of six on the entire pool).


X = Base Die Pool

E = Edge


In case of Adding Edge First (Gets Rule of Six):

(X + E) / 3 = Average hits

(X + E) / 6 = Average 6's that get rerolled.

((X + E) / 6) / 3 = Average hits of this reroll.


7(X + E) / 18 = Average Total Hits



In case of Rerolling Dice that didn't get hits:

X / 3 = Average hits.

2X / 3 = Average dice to be rerolled.

(2X / 3) / 3 = Average additional Hits.


5X / 9 = Average Total Hits



Set Average Total Hits of both to be equal...

7(X + E) / 18 = 5X / 9

7(X + E) / 2 = 5X

7X + 7E = 10X

7E = 3X

7E/3 = X


If your Base Die Pool is ~7/3 * your Edge (A little more than double), the average hits are the same.

Using an example: Edge of 6, a die pool of 14 would be a wash (7.77 hits).
If you increase the Die pool to 18: spending edge afterward gets you an average of 10 hits. Spending edge beforehand gets you ~9.33 average hits.

Decreasing base pool to 12: afterward is average 6.66, beforehand is 7 average hits.


My rule of thumb is if your base die pool is double your Edge or less, edge ahead of time. If your die pool is triple your edge or more, use edge afterward. In between, it's based on your luck.

The reason why I asked is in our last session a situation came up where my character's base dice pool was 21 dice and her edge score is 7. I really needed as many hits as possible (opposed test) and I was hard pressed to decide if I should add the edge before or re-roll. My typical roll for this test is 19 dice (+7) and I usually add the edge to the poll on start, but with 21 dice I couldn't figure out quickly which I wanted.

I ended up with the 28 dice Ro6 roll and barely beat my opponent (only 3 net hits). My dice were very much against me that day, which is actually pretty typical for me.

With this "lucky" build it is sometimes important to know when would be best to add or re-roll. I'm the only player that uses edge much, by the end of most missions I'm at 0 available edge. (IMG:style_emoticons/default/smile.gif)

As a general rule: if your dice pool is large, roll first and Edge later. You might get lucky without it. Also, you then have the advantage of knowing exactly how many more successes you need, so you can Edge appropriately.

You make it sound like you get a big benefit for just adding the edge pool after you've already rolled. You only get the rule of six on the edge dice if you're adding it after the roll has already been made, so it's not likely to have a big effect, even an edge of 6 is only likely to get one or two dice that get to be rerolled on a rule of six after the fact...

You do have a big benefit. Namely, you know how many more successes you need. If you spend before the roll, and your pool is large, you could end up with overkill.

Look at it this way. If you're rolling 21 dice, you stand a good chance of succeeding without Edge. If you do fail, you can count how many dice failed, compare that to your Edge score, and determine which gives you the most dice. For example, if you have Edge 6 and 10 failed dice, rerolling is the better choice. If only 3 failed, then Edging for extra dice is best. The Rule of Six is just a bonus.

I rarely know how many hits I need. In our group the GM rolls behind a screen (we like it that way). The process usually is: I roll and report my hits, then the GM reports the result.

There have been times when I didn't use edge and reported a more-or-less average roll, I said I would use edge and the GM suggested I not "waste" the point as I really didn't need it. I could have still used it for the better success, but usually when a suggestion of that nature comes in you follow it.

By the way, this whole thing is running off of a heavy-handed house rule to over-simplify matrix interaction. We have for the most part boiled hacking down to a single opposed test. Whomever gets more successes affects the other in a more dramatic way. If the "house" wind the worst-case is that the hacker suffers 10P damage (unresisted) and is tracked, the best case is the hacker has up to 4+ "commands" that can be done on the device and pulls pay data. No back doors are allowed. It works well for us.

While technically the GM isn't obligated to report how many successes he rolled on an opposed test, he is obligated to report degree of success. Based on that, you can easily estimate how many more successes you need after the roll. For example, if you're shooting at someone and the GM reports a narrow miss, it's pretty clear you are only a few successes off. If he reports a critical success, then you know you need at least four more successes, and so on.

That's what does happen usually. (IMG:style_emoticons/default/smile.gif)

Way back (years ago, I haven't the patience to search out the thread), a bunch of us used different methods, algebra, calculus, whatever, to arrive at the turning point ratio of 2.5. If the original dice pool is more than 2.5 times the Edge pool, the likelihood of more successes comes with rerolling misses. If the dice pool is less than that, the likelihood of more successes comes with adding the Edge dice before the roll.

Dumb-shit luck can blow any of this out of the water.

Thanks pbangarth, this is precisely what I was looking for. My dumb luck usually runs on the side of aww shit rather than woohoo.

Once the gm has announced the results of a test, it's usually too late to use edge to alter the results...

The degree of success of an opposed test is based on the compared rolls, once both parties have rolled and determined their results. Edge would have to be used before the results are determined, not after.

The books don't actually say that. All it says is "after you roll". So you can roll, wait until the GM announces the opposing successes, and and then spend Edge before the roll is resolved.

You must have a very liberal GM. When I announce the degree of success, the roll is resolved. You can spend Edge to reroll failures between rolling and getting the result, but once the result is in, it's in.

You're welcome to do that in your own games, but by RAW, it's not clear. Because I ran a lot of Missions games, I had to stick to RAW.