Calculating Lintner of a grain bill

So, if I understand correctly, a grain needs to have above 35 °Lintner to self-convert. Also, when using adjuncts, you need to raise the diastatic power of everything in the mash above this - ie, 1 pound of a 150 °Lintner 2-row plus 2 pounds of rice will have an effective diastatic power of 50 °Lintner. Is this correct?

How do you calculate this? It's easy when you just have one base malt plus adjuncts. Plus, I suck at math...

I did my first adjunct heavy beer this week, and it got me thinking. Search didn't turn up anything really useful, but I probably didn't use the exact right combination of search terms.

I think you are right that you can just average things, but only include the grains that need to be converted in the calculation (no dark roasted grains or crystal included, etc).

More complex example (making up numbers):

10 lbs of 2-row w/ Lintner of 45
1.5 lbs brown malt w/ Lintner of 0
1 lb of Biscuit Malt w/Lintner of 2

Mash Lintner = [(10*45)+(1.5*0)+(1*2)] / 12.5 = 36.16 Lintner

Walker said:

Mash Lintner = [(10*45)+(1.5*0)+(1*2)] / 12.5 = 36.16 Lintner

Click to expand...

That's what I thought, but I've never seen it printed anywhere. I suppose as long as you use the same weight units for everything?

I've never seen it listed out anywhere either... But tha above makes sense to me. I think the most inportant part is to know whether your grain does or does not need conversion. Those that don't should be excluded completely since they do not provide or need enzymes.