how to calculate expected FG based on reading from beginning of boil?

One of my problems has always been awful efficiency. Until I can work to fix it I was thinking of adjusting my mash by adding DME to compensate at the beginning of the boil to bring it up to the gravity it should be. Anyone know the math I should use to compensate based on a gallon per hour boiloff based on my original gravity readings before the boil?

It's all in the free "how to brew" by Palmer online

C1*V1=C2*V2. C=concentration(gravity) V=volume. Drop the decimal if you're using SG (so 1.045 would be 1045). Or just use this calculator: http://www.brewersfriend.com/dilution-and-boiloff-gravity-calculator/. I'm sure there's a bunch of other calculators online too.

peterj said:

Drop the decimal if you're using SG (so 1.045 would be 1045).

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you'd use 45, not 1045

dcp27 said:

you'd use 45, not 1045

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Whoops, you're right. My mistake.

Eddiebosox said:

One of my problems has always been awful efficiency. Until I can work to fix it I was thinking of adjusting my mash by adding DME to compensate at the beginning of the boil to bring it up to the gravity it should be. Anyone know the math I should use to compensate based on a gallon per hour boiloff based on my original gravity readings before the boil?

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I wouldn't add it at the beginning of the boil. Do your boil, take a gravity reading and see how many points you need. At this point you know your final volume and don't have to worry about boil off issues.

Add the appropriate amount of DME at flameout....dissolve well, take another gravity reading.

So lets say there are 6 gallons in the BK and the SG is 1.050.....but you want 1.060. So you need 10 more points. ppg = 10 points X 6 gallons = 60 ppg required. DME is 46 ppg so you would need 1.3 pounds (60/46) of DME to raise that 6 gallons to 1.060

Just use more grain if your eff is lower than expected.