What color will the beer be?

What SRM tells you

SRM, the Standard Reference Method of the American Society of Brewing Chemists, is a number for how much light a beer absorbs at one wavelength, 430 nanometers, in a standard cell. In the BJCP 2021 guidelines an American light lager is 2 to 3 SRM, the darker styles run well into the 30s, and the scale's own color list ends with black, opaque beer at 40 and above. It is a measure of the depth of color, not of its hue; the BJCP style guidelines say plainly that it should not be used alone to name a color.

The calculation

Malt color units: MCU = Σ (pounds of grain × its °Lovibond) ÷ gallons of beer. It is like the alpha acid unit of hops: a count of how much color goes into the batch. Morey's equation turns the count into SRM: SRM = 1.4922 × MCU^0.6859. For beers darker than about 50 SRM the fit is poor, so the page says so when you pass that point. EBC is SRM × 1.97.

Worked example. The Beer & Brewing example: 10 lb of 1.8 °L pale malt and 1 lb of 60 °L crystal in 5 gallons. MCU = (10 × 1.8 + 1 × 60) ÷ 5 = 15.6, SRM = 1.4922 × 15.6^0.6859 = 9.8, EBC = 19.3. In the calculator's starting values, 9 lb of 2 °L and 1 lb of 60 °L, MCU is 15.6 and the beer is 9.8 SRM, in the "amber" range.

Color ranges

The BJCP Beer Style Guidelines (2021) pair color words with numeric SRM ranges, which overlap and leave gaps, and tell judges to favor the words over the numbers when they conflict. We use the lower end of each range as a boundary, and the descriptions are our own.

Limits and common mistakes

A model of the grain bill, not of the beer. Brew Your Own lists the factors the equation ignores: boiling, heating, hopping, flocculation, clarity, age and oxidation, which together can move the real color by plus or minus 20%. A long boil or a late extract addition changes the color, and the estimate does not know it.

Mixing up volume. MCU divides by the volume of the finished beer, not the pre-boil volume or the mash water. Using 6.5 gallons in a 5 gallon batch makes the beer look 1.6 SRM paler than it will be.

Treating the ranges as exact. Above about 40 SRM judges cannot tell beers apart by eye, and an MCU of 200 is not twice as dark as an MCU of 100 (Brew Your Own).

Entering EBC in the Lovibond column. A malt label in EBC is a larger number than the same malt's Lovibond rating, so entering it as °L makes the beer look too dark. We have not verified a conversion between the two for malts, so enter °L as printed.

Frequently asked questions

How do you calculate beer color from the grain bill?

First work out the malt color units: for each grain multiply its weight in pounds by its color in degrees Lovibond, add them up and divide by the gallons of finished beer. Then apply Morey's equation, SRM = 1.4922 × MCU^0.6859. The Beer & Brewing example is 10 pounds of 1.8 °L base malt and 1 pound of 60 °L crystal in 5 gallons: (10 × 1.8 + 1 × 60) ÷ 5 = 15.6 MCU, which gives 9.8 SRM. The base malt alone would be 3.60 MCU and 3.6 SRM, so a single pound of crystal malt does most of the work.

Why not simply use MCU as the color?

Because color does not add up linearly. Doubling the malt color units does not double the darkness of the beer; Brew Your Own makes the point with a number: an MCU of 200 is not twice as dark as an MCU of 100. Morey's equation, with an exponent of 0.6859, takes that into account. For a pale beer the two are close, but MCU runs far ahead of SRM in a stout.

What is the difference between SRM and EBC?

They are two scales for the same measurement: the absorbance of beer at 430 nanometers in a cuvette. The American SRM multiplies the absorbance through a 1 cm cell by 12.7 (the ASBC method), the European EBC multiplies it by 25, so EBC = SRM × 25 ÷ 12.7 = 1.969, commonly rounded to 1.97. A beer of 9.8 SRM is 19.3 EBC. Brew Your Own calls the EBC rating "about twice the SRM rating". Both scales measure density of color, not hue or tint, which is why two beers with the same number can look different.

How accurate is the estimate?

Brew Your Own says that boiling, heating, hopping, flocculation, clarity, age and oxidation can put the real color about 20% above or below the figure from the grain bill. Morey's equation was fitted to beers lighter than 50 SRM (Beer & Brewing), so for very dark beers treat the number as an indication. Above about 40 SRM judges cannot tell beers apart by eye (Brew Your Own). To check a recipe, compare the beer with the color of a commercial beer you know, or measure a sample with a spectrophotometer at 430 nm.

Which color do I enter for a malt?

The °Lovibond rating on the maltster's data sheet or the shop's label, for example about 2 °L for pale two-row malt and 60 °L for a medium crystal malt. European maltsters give EBC. We have not verified a conversion between a malt's EBC and its °L rating, so this calculator does not convert one; look for the °L figure, or use the SRM of the beer after you have measured it. The BJCP style guidelines say Lovibond is roughly equal to SRM for all but the darkest beers, but that is a statement about beers, not an invitation to swap the two for malt ratings.

Sources: Beer & Brewing, "Seeing the Color in Your Future" (Morey's equation, the 5 gallon example; beerandbrewing.com); Brew Your Own, "Raise the Colors" (MCU, SRM and EBC, limits of the models; byo.com); ASBC Beer-10 and the Thermo Fisher application note SN53076 for the 430 nm definitions (read through the search summary and the application note; the ASBC method itself is paywalled and was not opened); BJCP Beer Style Guidelines 2021, Color Reference (numeric ranges only). John Palmer's How to Brew appendix gives the same equation rounded (1.49 × MCU^0.69); the site was not reachable when we checked. Neighbours: IBU calculator, ABV calculator, priming sugar calculator. How we check our calculators.