Originally By Tony Ackland

Yield from Grains

How much alcohol can you expect to make, based on your Grain recipe ?. Check out Mash Effficiency and Yield which I have stolen in its entirety, from a posting from John Palmer which was sent to the rec.crafts.brewing discussion group. Sorry, but its still in imperial units (points/pound/gallon (ppg)).

Whats the differences between 6 row and 2 row barley ? Dick explains ..
The numbers refer to the number of ears around the central stalk. Two row barley has the ears lying (believe it or not) flat in two rows either side of a central stalk while in 6 row barley the ears are all round the central stalk. The important difference is that 2 row barley tends to have a much lower nitrogen content than the 6 row and is therefore much more suitable for malting for brewing and distilling. A high nitrogen content in the barley results in a high protein/lower starch content in the malt/mash which in turn results in less ethanol & more higher alcohols + other nasties after fermentation. 6 row barley is used to produce bread flour etc., while whisky distillers/ maltsters will put very strict limits on the nitrogen & moisture content of any barley they buy. One of the reasons Scotland started producing such good spirits & beer was that 2 row barley would grow in our much poorer soils and needed much less fertilisation than 6 row.

A few weeks back I wanted to work out optimal vs actual conversion rates for a few different mashes. I converted a few of the points/pound/gallon rates on your mash efficiency and yield page to points/gram/litre, and thought I should send the formula through to you as well:

x p/p/g = x / 119.8264 p/g/l

e.g.:
1/2 kilo 2 row lager malt
3 kilos wheat flakes
17.5 litres of water

using the optimal column:
37 ppg for the 2 row is 37/119.8264 pgl, or .30878 pgl
36 ppg for the wheat flakes is .30043 pgl

500 gms x .30878 = 154.39
3000 gmx x .30043 = 901.29
total: 1055.68
1055.68 / 17.5 = 60.32 points
divide the actual number of points the mash yielded by 60.32 and you have your mash efficiency, just like using the original imperial rates in John Palmer's post.
It took me quite a while to find the correct conversion method so I thought it might help out someone else trying to do the same thing without thinking in imperial.
PS -- I assumed the author was using US Imperial units -- if you know that they were in fact UK units please let me know. The conversion factor in that case would be x/99.77633.