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I'm looking for some help trying to figure out the best way to measure the expected results of various blast and template weapons.

I've made diagrams trying to figure out how many models I could cover assuming the target is at base to base, 1" and 2" coherency and I've tried factoring in the various BS levels to get an approximate "chance to hit" blast weapons but it's still not nearly as clean as direct fire weapons.

Please share any calculations, rules of thumb or hard won experience you have with how you measure the effectiveness of blast and template weapons.

It is also wildly variable on how your opponent is a) able and b) willing to move their troops in spread formations.

My totally un-scientific, gut feeling, biased memory gives me these numbers. These assume BS4 marines under normal battlefield situations.

Small blasts can be generally be relied on to catch 2-3 models. Anything more then that is gravy. I use 3 as the number hit when I'm doing my back of the envelope level math hammer. This assumes, of course, that your scatter die is more corporative then mine. The moody, fickle little <beep>. In play, I assume that every small blast will scatter in the worst possible direction, and miss anything relevant. I don't use a whole lot of frag missiles.

Flamer templates I use 4-5 as my average number. This number is probably a bit low, and is very situationally dependent. Sometimes you only get 3, others a whole 10 man squad. Highly mobile templates can be put down just so, giving speeder and jump pack deployed ones a much better hit ratio then footsloggers.

Large templates bring us back to the accursed scatter die. I don't use these often, so don't have a good feel for them. In general, if my opponent is using them, I assume the whole darn squad is going away. The way my scatter rolls, I'd probably assume 5-6 hits under the pie plate for when I field them.

I usually use assumed numbers of hits for all the BS. BS is much less important for blast weapons than for regular shots.

BS<5
Small Blast: 1.5 models
Large Blast: 2.5 models

BS doesn't matter for templates
Template: 4 models
Torrent: 6 models

BS>5
Small Blast: 2.5
Large Blast: 3.5

If I want to speed the calculation up then I round down so I will usually be pleasantly surprised by the outcome.

Great help so far. This is exactly what I was hoping for.

Since it is quite the struggle to accurately calculate the expected outcome, rules of thumb and experience seem to be the best hope for in game decision making.

Keep it coming.

Blast/Template weapons can be tricky to calculate the number of hits.

Normally you can expect to get 2-3 under a blast template, but then there is the risk of a scatter. Since 2/3 of the scatter dice results are a scatter and not a 'HIT' then the majority of time you will be scattering. Even subtracting the BS from the roll odds are your blast will not land where you wanted it to.
That's why I give a ratio of 1.5 hits with a blast template and 2.5 models under a large blast.

Template weapons are much more reliable. Its very easy to get them under a template. I give 5 models to a template, as its very easy to get them lined up properly.

Shall we scale up to apocalypse/deathstrike blasts? Although I don't think any amount of spreading is going to stop a 10' blast from wiping your squad.

At best you can try to estimate there are far too many variables to accurately get any kind of results. Damage from a blast depends on

1.) Number of models covered.
2.) Position of the blast within the squad
3.) Scatter result
4.) BS
5.) Size of squad/ footprint
6.) Spread between models
7.) Direction of scatter
8.) Base size of models.

So we need to make some assumptions in our calculations.

Lets assume for instance that your small blast will catch 3 models if a hit is rolled. or if the scatter = your BS. If the scatter is 1-2" in any direction lets assume you hit 2 models, if it is 3 -5 you hit 1, 6+you hit nothing. Obviously this is not always true, sometimes scattering in a direction will hit more models, somteimes you can scatter 6" and still hit models etc. But there is no way to know that in your analysis.

So for BS 4 model with a small blast.

1/3rd of the time you roll a hit. 2/3rds you scatter. 1/6th of the time you scatter you will still get 3 hits. 1/4th of the time you scatter it will be 1-2" so you still get 2 hits. 15/36 of the time you will be scatter 3-5", netting 1 hit. The rest of the time you miss completely.

Based on this you end up with 0.444(3)+2/3(1/6)(2)+15/36*2/3(1)= 1.94444 hits on average.

GIven that the 1.5 hits is not a bad esitimate for a small blast (as it is conservative).

Another odd thing is that with a unit spread out at max coherency you will get more hits with a 1-2" scatter than you will with a direct hit or a 0" scatter.

With 25mm bases at max coherency, a direct hit will only get the guy you were targeting. Assuming you had the blast centered on the target and not off center.


There are too many variables to consider the accurately predict the amount you can hit with blasts.

Nobody will have the time or precision to get all their models at maximum coherency is the biggest reason. Plus if the scatter dice comes up with an arrow, there is 360 degrees of direction the arrow could possibly point to.

Another thing to consider is what kind of blast template you are using. If I have a missile launcher, and someone is at max 2" coherency, I don't even think about lobbing a frag downrange. I don't care if they are grots, they are eating a krack missile and I'm killing one of them guaranteed,

Now when I've just wrecked someone's ride, and they are packed in base to base in a tight little bunch in the crater, or just deep struck down, the frag starts to call to me. As long as I don't scatter -too- much, I can still get a huge number of hits! And then I shoot that tree over on the left. I regret every frag I fire.

I shouldn't say that. I did have one game where my typhoon/HB speeder did some very unkind things to some gaunts. But that was an exception, not the rule.

I guess my point here is that if you have different fire modes, like a missile launcher or a fire prism, the dispersal of your target can make a huge difference with what mode you use. Do you take the one reliable kill, or the chance of two or more? Situations like the nature of the closest model (sarge/heavy gunner) or number of wounds (is this going to be the casualty that forces the Ld test?) can make it more important to guarantee at least one kill over the chance of larger carnage. So in situations where the numbers are iffy for the blast, they often don't get used. They only get shot into "ideal" situations.

Someone on ATT with smarts and time on their hands did some fun calculation work for blasts and came up with some general principles.

For Blasts/Large Blasts and BS 3, you would score .5 hits for each model you placed the template over. At BS 4 this was .6 hits and BS 5 it was .7 hits.

Don't recall any flamer work, but the above can be used for some Mathhammer.

 Nevelon wrote:

I guess my point here is that if you have different fire modes, like a missile launcher or a fire prism, the dispersal of your target can make a huge difference with what mode you use. Do you take the one reliable kill, or the chance of two or more? Situations like the nature of the closest model (sarge/heavy gunner) or number of wounds (is this going to be the casualty that forces the Ld test?) can make it more important to guarantee at least one kill over the chance of larger carnage. So in situations where the numbers are iffy for the blast, they often don't get used. They only get shot into "ideal" situations.

Very good point. It doesn't affect single fire model weapons but if you're given the choice between a blast and direct fire weapons, it does make sense to consider the target's disposition.

I am generally distrustful of small blast templates in general. They just look too weeny to be of any use whatsoever. I think I'm just spoiled though since I started playing Tau back when all we had were large blast templates. That said, if I keep getting the results. I have been getting out of my ion rifles I might change my mind.

Also, here's something relevant to the discussion. Just ignore some of the probability and you should be fine. Knowing this helps immensely in guessing how effective your blast will be since you'll know base size and template size.

http://www.filedropper.com/scatter-bs (sorry for the shady file upload site, the original is behind a login gate at BoardGameGeek if you want to look for it)

 dementedwombat wrote:
I am generally distrustful of small blast templates in general. They just look too weeny to be of any use whatsoever. I think I'm just spoiled though since I started playing Tau back when all we had were large blast templates.

That is my gut feeling as well.

The fact that the 1.5" radius is smaller than the max coherency is a major turn off for me mentally.