Top-down Brew: Grain Weights to Percentages

Purpose: Convert weight grain bills to the format used in the beer engine recipe calculator

Enter weight and select the malt type. The empty field on the right is for entering custom yield in either specific gravity or coarse-grind as-is percentage.

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Results

Discussion

This calculator converts standard recipe grain bill weights into percentages and values needed for the beer engine calculators. The percentages are based upon each malt or sugar's gravity point contribution to the wort divided by total gravity points.

The format needed for the precise calculator is ...

malt: name, percentage, lovibond, yield 

OR 

sugar: name, percentage, lovibond, yield

Legend:

name: The common or commercial name of the malt or sugar
percentage: proportion of the wort composition by gravity points expressed as a percentage
lovibond: color in the lovibond scale
yield: maximum theoretical yield expressed as a percentage or specific gravity

Percentages by gravity and percentages by weight are similar, but not exactly equal because various malts or sugars contribute less or more to gravity points to the wort for an equal weight. For example, 1 pound of sugar contributes more gravity (1.046) than 1 pound of malt (1.037). A hypothetical grain bill of 10% sugar (sucrose) by weight and 90% two-row malt will make a wort that is 15.4% sugar in regard to gravity.

The calculations adjust the mashed grains downward based upon mash efficiency. Most recipes assume a mash efficiency. For example, the recipes published in BYO magazine assume a 65% mash efficiency. This adjustment is not necessary for sugars.

Malt yields can be expressed as either percentages (example: 80%) or specific gravity (example: 1.037).

The weight units - metric or US - and batch volume are not necessary calculating percentages. The gravity point concept is really a non-metric method (points per pound per gallon), but the proportions calculated will be accurate with either system for the purpose of this calculator.