The color of brew can be estimated if one knows the color and quantity of the malts used. There are a two methods for estimating color, but the latter equation by Dan Morey is accepted to be the more accurate of the two. To use either method, you do need to know the Lovibond (SRM) color for each ingredient. Several reference tables are available on the Malt page to tell you the color for different types of malt.
Malt Color Units
The simplest equation for estimating the color of beer is to use Malt Color Units (MCU). A malt color unit is defined to be simply the color of each grain times the grain weight in pounds divided by the batch volume in gallons. If more than one grain is used, the MCU color is calculated for each addition and then added together. This malt color unit equation provides a good estimate of color in SRM for beers that are light in color (SRM color < 10.5).
- MCU = (color * grain_weight_lbs)/volume_gallons -- Good for beer colors < 10.5 SRM
The Morey Equation
While MCU is a good estimate for SRM beer colors < 10.5, the MCU color overestimates the color value for darker beers. In an article on Brewing Techniques Dan Morey proposes using a slightly more complex equation based earlier work and raw data by Mosher and Daniels to handle darker beers. This equation holds for values of SRM up to 50. Most beer software uses the Morey equation. The Morey equation is derived from the MCU value calculated above.
- SRM_Color = 1.4922 * [MCU ^ 0.6589] -- Good for beer colors < 50 SRM