Starting gravity calculation?

just out of curiosity how do u calculate starting gravity with out taking a hydrometer reading?

I think DME is rated like .8% per pound, but you really have to know the volume of water also.

Grains and extracts have an "extract potential," which is the resulting gravity if you added one pound of the extract (or specialty grain) in question to a gallon of water or mashed one pound of the base grain into a gallon of water at 100% efficiency. You take that extract potential number and do a little algebra.


TL

You could also use brewing software.

For free: http://hbd.org/cgi-bin/recipator/recipator

GT

Extract or grains?
Multiply the number of gravity points per pound per gallon by how many pounds you are using and divide by them number of gallons you are making.

Example:
6 pounds LME (at 34 gravity points per pound per gallon)x6lbs=204 gravity points.
204/5 gallons=40.8
So with 6 pounds of LME you will have about a 1.041 beer.

If using grains you need to know your efficiency. Say the grains have a potential of 37 gravity points per pound per gallon and your efficiency is 70%.
6 pounds grainx37(gravity points per pound per gallon)x0.7(efficiency)=155.4
155.4/5 gallons=31.08 or a SG of about 1.031.

http://beertools.com/html/calculator.php

Free and easy.