Thanks for the idea. I think the math isn't quite right since the OG was supposed to be 80 with 5.25 gallons of water the whole time, but when I follow along the same idea I think the boil over accounts for the difference.

LME * Water * X = OG where X is the factor that converts the LME to Water to an OG.

Initial Plan: 12 * 5.25 * X = 80

X = 80/(12*5.25) = 1.2698

Since I estimate I lost a quarter ounce during the partial boil (now that I know the terminology correctly) I take a ratio of my initial LME to account for the loss. I later added enough water to get back to 5.25 so that inputs stays the same.

Actual Execution: (3.75/4*12)*5.25* 1.2698 = 75

Given that I'm at about 77 now I must not have lost a full quarter gallon. For curiosity sake:

(Y/4*12)*5.25*1.2698 = 77

Y = (77/(5.25*1.2698))/12*4 = 3.85

So I *only* lost 0.15 gallons in my boil over and the other 0.1 gallons was likely just the water boiled off. That probably explains my low OG.

any ideas why the

Brewer's Friend Extract Calc would over estimate the OG to be 85 with 5.25G water and 12 lbs LME? I've found the other calculators to be pretty good, but this seems abnormally off to me. I wonder if there are issues at higher gravitys.