The Home Brewing Recipe Calculator
by John Palmer, author of How To Brew

The HBRC is a complete beer recipe calculator. With it you can quickly determine the recipe gravity from different malts and extracts, and the bitterness contributions from different hop additions, for any batch size between 5 and 12 gallons.

Side One offers two functions: a Gravity-Volume Converter, and a Gravity Contribution Calculator. The gravity-volume converter is useful for figuring the change in your wort gravity between the initial boil volume and your final recipe volume (OG). Simply line up the scales for the initial volume and gravity readings (Slide A), and read off the corresponding gravity at any other volume.

The Gravity Contribution Calculator works similarly. Simply line up Weight scale to the Yield of a particular ingredient, and read its gravity contribution on the scale below as a function of wort volume. For instance: One half pound of Steeped Crystal Malt yields a gravity of 1.003 at 3 gallons, 1.0045 at 2 gallons, and 1.006 at 1.5 gallons according to the scale.

The calculator can also be used in reverse: To add five gravity points to a volume of 3 gallons for example, align the Volume/Gravity scale (Slide B) to those values and read the required weights of the various ingredients on the Weight/Yield scale above.

Side Two is a Hop Bitterness Calculator that determines the IBUs as a function of boiling time and boil gravity. Like the gravity calculator, it can be used to figure out how much hops to use to obtain a particular IBU level, or in reverse to determine the IBU contribution from a particular hop addition. A list of common hop varieties and their typical % Alpha Acid values is included for reference.

For example: For your second hop addition, you want to add 20 IBUs. You plan to boil the hops for 30 minutes and you know the gravity of your boil is about 1.050. How much of what variety of hops should you use?
Use Slide A to set the Boil Time (30) opposite the Boil Gravity (1.050). Next, move Slide B to set the desired IBUs opposite the Recipe Volume (ex. 5 gallons), without moving Slide A. The lower scale now shows you the required weight of hops to add as a function of the amount of alpha acids in the hop. For instance, if you planned to use Amarillo at 8% Alpha for this addition, the scale shows that .94 ounces would be required. If Liberty (3%AA) were chosen, 2.5 ounces would be required.

Alternatively, the steps may be reversed to calculate how many IBUs will be contributed from a particular hop addition. If you have 1 ounce of Cascade at 7.5% AA that is going to be boiled for 30 minutes at a boil gravity of 1.050, and the recipe volume is 8 gallons, the IBU scale shows that 12.5 IBUs will be contributed (or 10 IBUs if the recipe volume was 10 gallons).

The Home Brewing Recipe Calculator - a convenient alternative to having a computer at the kettle, or while selecting ingredients in the brewshop. Ask for it at your favorite homebrewing supply shop, or you can order it direct from the publisher. $7.95 List Price