Short answer
SRM and EBC both measure how much deep-blue light at 430 nm a centimetre of beer absorbs, then multiply by a factor: 12.7 for SRM, used in the US, and 25 for EBC, used in Europe. Because only the factor differs, EBC is about 1.97 times SRM. The number describes how dark a beer is, from pale straw lagers at 2–3 SRM to stouts at 30–40 and beyond, but not its exact hue.
In the laboratory a clear beer sample goes into a 1 cm cell and its absorbance of 430 nm light is measured. Multiply by 12.7 and you have SRM, the ASBC's Standard Reference Method; multiply by 25 and you have EBC colour. Dark beers absorb too much to measure directly, so they are diluted and the result multiplied by the dilution factor. The ratio of the factors, 25 ÷ 12.7, is 1.97, which is why EBC is quoted as roughly double SRM. Older recipes and malt specifications still use degrees Lovibond, which is close to SRM for all but the darkest beers.
Measuring at one wavelength captures darkness well, because beer's absorption falls steadily from blue to red, but it cannot distinguish a reddish amber from a golden one of the same depth. Two beers at 12 SRM can look noticeably different, one copper, one brownish, depending on the malts and any added colour. The number is also for a fixed path: the same beer looks darker in a wide glass than a narrow one because the light passes through more of it, and a stout that is 'black' in a pint glass can glow ruby at the thin edge.
The BJCP estimates that matching beer against a printed guide by eye gives errors of about 15% of the SRM value in daylight, rising to about 20% under tungsten light.
Beer judges estimate SRM with printed colour guides. The BJCP's guide was built from spectral measurements of around a hundred beers, and its patches assume a 5 cm path viewed in daylight against white. The instructions are practical colour science: use a container 5 cm wide or look down through 5 cm of beer, use daylight or a high-CRI lamp between 5000 and 8000 K, keep the beer and guide in the same light, and match lightness rather than hue. Colour-blind judges can use the guide but should expect more difficulty; lighter beers below about 10 SRM are easiest to match.
Style guidelines attach SRM ranges to each beer style — a German Pils at 2–4, an American amber ale at 10–17, an American stout at 30–40. These are competition conventions describing what judges should expect, not measurements of what breweries sell, and neighbouring styles overlap. Colourwise groups those ranges into seven broad bands for the colour-scales tool; the bands are a reading aid, not a published scale, and the table below shows the style anchors they were grouped from.
| Band | SRM | EBC (× 1.97) |
|---|---|---|
| Pale straw to straw | 0–3 | 0–5.9 |
| Yellow to gold | 3–6 | 5.9–11.8 |
| Deep gold to amber | 6–10 | 11.8–19.7 |
| Amber to copper | 10–17 | 19.7–33.5 |
| Copper-brown to brown | 17–25 | 33.5–49.3 |
| Dark brown | 25–35 | 49.3–69 |
| Very dark brown to black | over 35 | over 69 |
| Style | SRM range | Colour words (shortened) |
|---|---|---|
| 1A American Light Lager | 2–3 | very pale straw to pale yellow |
| 5A German Leichtbier | 1.5–4 | pale straw to deep yellow |
| 5D German Pils | 2–4 | straw to deep yellow |
| 5C German Helles Exportbier | 4–6 | medium yellow to deep gold |
| 18A Blonde Ale | 3–6 | light yellow to deep gold |
| 18B American Pale Ale | 5–10 | pale gold to amber |
| 19B California Common | 9–14 | medium amber to light copper |
| 19A American Amber Ale | 10–17 | deep amber to coppery brown |
| 13B British Brown Ale | 12–22 | dark amber to dark reddish brown |
| 6C Dunkles Bock | 14–22 | light copper to brown |
| 13A Dark Mild | 14–25 | copper to dark brown or mahogany |
| 19C American Brown Ale | 18–35 | light to very dark brown |
| 20A American Porter | 22–40 | medium to very dark brown, can approach black |
| 20B American Stout | 30–40 | usually jet black, sometimes very dark brown |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactModerate evidence
SRM is the absorbance of beer at 430 nm through 1 cm multiplied by 12.7; EBC colour is determined the same way with a multiplier of 25, so EBC ≈ SRM × 1.97.
Source: BJCP Color Guide
FactModerate evidence
The BJCP colour guide's patches were calculated from spectral absorption measurements of about 100 beers for a 5 cm path in daylight, and it estimates visual errors of about 15% of the SRM value in daylight and 20% under tungsten light.
Source: BJCP Color Guide
ConventionModerate evidence
BJCP 2021 style guidelines give colour ranges in SRM for each style, for example 2–4 for German Pils, 10–17 for American Amber Ale and 30–40 for American Stout.
Source: BJCP 2021 Beer Style Guidelines
Colourwise analysisLimited evidence
Grouping BJCP style colour ranges gives seven broad SRM bands from pale straw (up to 3 SRM) to very dark brown and black (over 35 SRM).
Based on: Colourwise grouped the colour words and SRM ranges of fourteen BJCP 2021 styles into contiguous bands; band edges are Colourwise's choice where style ranges overlap.
Caveat: A reading aid, not a published scale; different groupings are equally defensible.
Source: BJCP 2021 Beer Style Guidelines
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.