Beer Color Calculator (SRM & EBC)

How do you calculate beer color from a grain bill?

Every malt carries a color rating in degrees Lovibond (°L) — 2 for pale malt, 40 for a mid crystal, 350 for chocolate, 500 for black patent. Multiply each weight by its rating, add the bill up and divide by the batch volume, and you have malt color units:

MCU = Σ (lb × °L) ÷ gal In kg and liters, multiply by 8.35 — the same factor that turns PPG into points per kilo per liter.

MCU is not the color. Light absorption compounds — each extra bit of dark malt absorbs a share of what is left, not of the original — so beer color rises more slowly than the malt units do. Dan Morey fitted a power law to the published data, and it is the formula every calculator on the web now runs:

SRM = 1.4922 × MCU^0.6859 Stated to hold to 50 SRM, which is beyond every style guideline. EBC = 1.97 × SRM.

So 10 lb of 2-row at 2 °L with 1 lb of crystal 40 in 5.5 gal is 10.9 MCU — 7.3 of it from the single pound of crystal — and 7.7 SRM (15.1 EBC), which the style guidelines call amber. The stout below it — 8 lb pale, a pound of roasted barley, a pound of crystal 60 — is 68 MCU and 27 SRM, dark brown. Counted as MCU it would be 68, off the top of every chart.

Morey vs Daniels vs Mosher: why three formulas, and which is right

Two older fits are still printed in books. Randy Mosher's is SRM = 0.3 × MCU + 4.7; Ray Daniels' is SRM = 0.2 × MCU + 8.4. Both are straight lines, and a straight line with an intercept has a floor: no bill, however pale, can come out below 4.7 SRM on Mosher or 8.4 on Daniels. Ten pounds of pale malt on its own is 3.6 SRM by Morey — a straw-colored beer — and 5.8 on Mosher, 9.1 on Daniels, which is a gold beer that pale malt cannot make. That is exactly why Morey went back to their raw data and fitted a curve through the origin.

SRM by each fit. Dimmed cells are outside the range the linear fit was stated for (Daniels 10.5–37 MCU, Mosher up to 37). The two lines cross at MCU 37, at 15.8 SRM — which is where their range ends and where Morey reads 17.8.

The folk rule that MCU equals SRM for pale beers is exact at one point — 3.6 MCU — and is already three SRM high by 10.5, the top of the range it is usually quoted for. Morey's curve is below the 1:1 line everywhere above that. This page headlines Morey and shows the other two beside it, the way the IBU page shows Rager beside Tinseth: not because Morey is beyond question, but because the recipe you are copying may have been designed on one of the others, and the difference is the whole gap between an amber and a pale ale.

SRM to EBC and Lovibond: what the three scales mean

SRM (Standard Reference Method, the American scale) and EBC (European Brewery Convention) both measure the same thing — light absorbed at 430 nm — and differ only in the path length and a constant: EBC = 1.97 × SRM, so a 27 SRM stout is 53 EBC. Lovibond is the older visual scale, and it is what maltsters still print on the bag. For beer the two are close but not equal (SRM = 1.3546 °L − 0.76), and that formula is a trap: Morey's fit was built with malt colors in °L, so you feed the bag's number straight into the MCU. Convert first and a 500 °L black malt becomes 677 on the beer scale, and the color is counted one and a third times.

The bigger uncertainty is the bag itself. Chocolate malt is 350 °L from one maltster and 420 from another; crystal "60" ranges 50–70 by lot. Half a pound of chocolate at 420 °L instead of 350 moves the stout by 1.9 SRM on its own, which is why every row in the calculator lets you overwrite the °L with the figure on your analysis sheet.

Beer color chart: SRM by style

The descriptor bands are the ones the BJCP style guidelines use to translate a number into a word; the style ranges are the guidelines' published numbers. The swatch is what a beer at the middle of the range looks like through a pint glass, computed the same way as the calculator's.

BJCP 2021 ranges, rounded. Descriptors: straw to 3, yellow to 4, gold to 6, amber to 9, deep amber / light copper to 14, copper to 17, deep copper / light brown to 18, brown to 22, dark brown to 30, very dark brown to 35, black to 40, black and opaque above 40.

How much dark malt does it take to darken a beer?

Run the formula backwards: the MCU a target color needs is (SRM ÷ 1.4922)^1/0.6859, subtract what the bill already has, and divide by the coloring malt's °L. To take the 7.7 SRM pale ale to 14 — a copper amber ale — takes 0.70 lb of crystal 120, or 3.8 oz of chocolate malt, which colors without the caramel sweetness. The calculator's "reach a target" mode does this for whatever malt you name, and refuses to print a negative weight when the bill is already past the target — the answer then is less roast, not a calculator that invents one.

Because of the exponent, the first ounce of black malt does far more than the last: the same 3.8 oz that lifts a pale ale six SRM would lift the stout by about a fifth of that. Darkening a dark beer is expensive in roast, and the roast brings flavor the color chart never mentions — which is why a black IPA leans on dehusked Carafa and a brown ale on crystal rather than chasing the number with black patent.

Why does my beer look darker than the calculator said?

Usually it doesn't — it looks darker than you expected, which is a different complaint. In order of how often each one is the answer:

1. The glass. See the box below. A porter in a pint is black; the same porter in a taster is ruby. Neither is wrong.
2. The volume. The stout bill into 5 gal is 28.9 SRM; into 6 gal it is 25.5. A gallon of extra wort is worth 3.4 SRM, and a short boil or a generous sparge lightens the beer the same way it lowers the gravity.
3. The lot. The 1.9 SRM from a darker chocolate malt, above. Check the bag.
4. The boil. Long, hard boils caramelize wort and darken it. Palmer puts the whole prediction at about ±20 %, and this page does not model the kettle — no published formula does it honestly.
5. Haze and yeast. Suspended solids scatter light and read as darker and duller. The calculator predicts a clear beer.

The honest reading of all this: a color prediction is for landing inside a style range, not for matching a photograph, and two beers a couple of SRM apart are indistinguishable in the same glass under the same light. Use the number to keep a pale ale pale and a brown ale brown, and let the glass do the rest.

MCU to SRM chart, and malt colors (printable)

For recipes sketched on paper: MCU is easy arithmetic and the power law is not. Read the SRM across, with the EBC and the descriptor, and the typical °L of each malt beside it.