Grain to/from Malt Extract Conversion
Conversion from extract to grain or vice-versa is the most difficult. That's not because it involves complex math, but because extract manufacturers don't share the recipe for their extract wort. That means you won't know for certain which grains were used or in what amounts. All you can really do in these cases is approximate. BYO Magazine suggests that you can use specialty grains to closely approximate any malt extract on the market.
For light malt extract, the basic conversion is:
- Look at the specifications for the light malt extract. Find the points per pound figure. This will usually be 36 (1.036).
- Look at the specifications for the two-row malt grain. Identify its points per pound figure.
- If your brewhouse efficiency is 75% (which is common), your yield is 75% of the figure in the previous bullet.
- Multiply the weight of extract by the ratio of points from extract over points from grain.
For example, for 9 pounds of light malt extract (at 36 points) converts to 2-row pale malt grain (36 points x 75% efficiency = 27 points) as below:
9 pounds malt extract x (36 points extract / 27 points grain) = 12 pounds of grain
Thus, you'll need 12 pounds of 2-row malt to equal 9 pounds of extract, at a 75% efficiency.
To go the other direction, you would modify the calculation:
12 pounds 2-row x (27 points grain / 36 points extract) = 9 pounds of extract
If you're looking at a more complex extract like Amber, Dark, or Wheat, you have a lot more work to do. The BYO Magazine article linked above explains the process better than I can. It boils down to examining the manufacturer's specifications for the extract and inferring what you can from it about the grains they used to make it.
Convert DME to LME, LME to DME
The main difference between DME and LME is the amount of water. Water content in LME tends to be around 20%. In DME, it's essentially zero.
To do the conversion, 1 pound of a DME is approximately 1.2 pounds of an LME.