Can't Figure It Out

The last couple of batches, has me scratching my head. I get my pre-boil gravity and volume, but after I boil, my volume is where it should be, but my gravity is not.

Take the batch I just made. The pre-boil gravity was to be 1.030 and I hit 1.032 with a volume of 6.8 gallons. After all was chilled and put into the fermentor, I had 5 gallons and my gravity should have been 1.037, but I only got 1.034. Maybe I am splitting hairs here.

I would say that the difference is close enough. 1 quart will make a difference of about 1.003. So if your kettle and fermenter calibration are not exact, then your SG will be off +- a few points. It sounds like you got yourself an extra beer in the batch and thats not a bad thing! RDWHAHB
Cheers
Preston

You are correct about the exact calibration. I did pour 1 gallon at a time into my fermenter and then marked the location. I could easily have had a quart difference. Thank you so much.