Recipe conversion help

I got a british style bitter recpie from a podcast and the grains were given in %, how do you convert to a 5 or ten gallon batch. The first percentage is 83.5%.

Also the uk recpie mentions an amber malt? Is there another name for it here or where could I order it from.

Cheers

I'm nerding out here, but if you have the %'s, you should be able to set up a series of linear equations that also uses the theoretical gravity points per grain type, typical efficiency, and the target gravity and solve for the different variables representing lbs of grain per type. If I had more time to slack off at work, I'd try to work it out right now. Good luck!

What is the staring gravity? You can't know the amounts of each grain if you don't have a gravity to base it off of. Effeciency matters also.

Example:

5 gallon batch, 1.050 starting gravity

Pale Malt - 80%
Crystal 40 - 10%
Crystal 80 - 5%
Aromatic Malt - 5%

Let's say your base malt has an extract of 1.037 ppg (points per pound, per gallon). That means at 100% efficiency, you would need approximately 6.75 lbs of malt to get a 1.050 gravity.

(50 total points divided by 37 points mulitplied by 5 gallons)

(50 x 5)/37 = 6.76

Now that is a theoreticall number becuase you will never get 100% extraction out of the malt, so let's assume an average of 75% effiviency.

pounds x 75% = 6.76

6.76/0.75 = 9.01 pounds

Basically you need 9 pounds of grain at 75% efficiency to get a 1.050 gravity.

Now let's get the percentages

10% is 0.9 lbs
80% is 0.9 x 8 or 7.2 lbs
5% is 0.45 lbs

7.2 lbs Pale Malt
0.9 lbs Crystal 40
0.45 lbs Crystal 80
0.45 lbs Aromatic Malt


The short answer in all this is to get some brewing software that will do all the calculations for you and you can see the percentages and efficiency numbers and be able to adjust the quantity of any ingredient to get what you want.