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SRM and EBC: how beer colour is measured

The colour of beer is the first thing we see when raising a glass - from the straw yellow of a pale lager, through amber and copper, to the deep black of a stout. But behind what seems a simple observation stands a whole science of measurement. The colour of beer is measured objectively, in standardised scales: SRM, EBC and degrees Lovibond. Thanks to them breweries can precisely determine and reproduce the colour of beer, regardless of the subjective eye. In this post you will get to know these three scales, learn where they came from, how they convert, how colour is calculated from malt and why objective measurement replaced eyeballing. It is a journey into the science of beer colour. Let us start with where the colour of beer comes from at all.

Where the colour of beer comes from

The colour of beer comes above all from the malt, specifically from the degree of its kilning. Pale malts, dried at a low temperature, give straw and golden beer. Darker malts, roasted and burnt, give amber, copper, brown, and in the extreme black. Responsible for these dark colours are Maillard reactions and caramelisation occurring during malting and roasting, creating coloured compounds called melanoidins. The more strongly kilned the malt, the darker the beer. Therefore the colour of beer is largely a reflection of the malt used: a pale lager is made from pale malt, and a black stout from roasted malt and barley. Colour also depends on the proportion of dark malts in the grist - just a little roasted malt is enough to darken a beer strongly. Understanding that colour comes from malt is the key to how it is measured and predicted. The colour of beer is not chance, but the result of the recipe. So let us get to know how this colour was measured historically, starting with the Lovibond scale.

Degrees Lovibond - the beginning

The first method of measuring beer colour was the Lovibond scale, the foundation for later systems. Joseph Williams Lovibond, an English brewer, created the Lovibond Tintometer in 1885 - an optical device that compared a beer sample against coloured glass slides. The brewer adjusted the slides until the colours matched, and the result gave the colour of the beer in degrees Lovibond. It was a subjective method, relying on the human eye comparing samples. Despite this it was a breakthrough: for the first time it allowed the colour of beer to be expressed numerically. The Lovibond scale has survived to this day, although in a changed role. In the US Lovibond units are still used to quantify the colour of malt and extracts, while SRM is used to quantify the colour of wort and beer. Degrees Lovibond are the historical beginning of colour measurement, the foundation on which the modern, objective scales were built. It is a heritage of 19th-century brewing, still alive in the measurement of malt. So let us get to know the scales that grew from it - SRM and EBC.

SRM - the American scale

SRM (Standard Reference Method) is the American, modern scale of measuring beer colour, which replaced subjective judgement with a precise instrumental measurement. SRM cuts out the subjectivity of choosing colours by relying on instruments instead of the human eye. The measurement involves passing light of a particular wavelength through a beer sample and measuring how much light is absorbed - the darker the beer, the more it absorbs, and so the higher the SRM value. The SRM scale stretches from very low values for pale beers to high for dark ones. A pale lager is about 2-4 SRM, an amber ale 9-14 SRM, a brown porter 20-30 SRM, and a black stout 30-40 and more SRM. SRM is today the standard of measuring the colour of beer and wort in the US, giving objective, repeatable results. Thanks to it brewers can precisely determine and reproduce the colour of beer. SRM turned the subjective impression of colour into a measurable, scientific value. It is the foundation of modern beer colour control.

EBC - the European scale

EBC (European Brewery Convention) is the European equivalent of SRM, used in Europe to measure beer colour. It measures the same phenomenon - the absorption of light by beer - but expresses the result in a different numerical scale. Key is the relationship between the two systems: the EBC colour is approximately 1.97 times the SRM colour. In other words, EBC equals about 1.97 multiplied by SRM, which in practice means that EBC values are roughly twice as high as SRM for the same beer. So a pale lager of 3 SRM is about 6 EBC, and a dark stout of 35 SRM is about 69 EBC. Beyond the different numerical scale, EBC and SRM are in essence the same measurement of the same phenomenon. European brewers use EBC, American ones SRM, but both describe the same colour. Knowing the conversion (about 2 times) lets you easily move between the scales. EBC is the European language of beer colour, equivalent to SRM. They are two dialects of the same scientific measure of colour.

How colour is calculated from malt

Brewers can predict the colour of beer even before brewing, calculating it on the basis of the malt used. The MCU method (Malt Color Units) serves this. MCU is the colour of each malt in degrees Lovibond multiplied by its weight in pounds, divided by the batch volume in gallons. In other words, the colour contribution of each malt in the grist is summed. The problem is that MCU estimates the SRM colour well only for pale beers, and begins to diverge when the colour exceeds 6-8 SRM, because the absorption of light is logarithmic, not linear. Therefore for darker beers the more accurate Morey equation is used, which gives an excellent estimate of colour throughout the range from 1 to 50 SRM and is used today by most brewers. Thanks to these calculations the brewer can design a beer of a desired colour, choosing malts before even starting to brew. Calculating colour from malt is a practical tool of designing beer. It is science in the service of the recipe. We write more about the role of dark malts in our post on dark beers.

Why measure colour

One might ask: why measure the colour of beer so precisely? There are several reasons. First, repeatability: objective measurement lets you reproduce exactly the same colour batch after batch, which is key for the consistency of a brand. Second, conformity with style: many beer styles have defined colour ranges (for example a pilsner must be pale, and a stout black), and measurement lets this be controlled. Third, communication: the SRM and EBC scales give a common, objective language of describing colour between breweries, competition judges and customers. Fourth, design: calculating colour from malt lets you design a beer of a desired colour before brewing. Fifth, quality control: a deviation of colour can signal an error in the recipe or process. Measuring colour is not pedantry, but a practical tool of modern brewing. Replacing eyeballing with an objective scale is part of the professionalisation of the industry. Why measure colour? Because precision gives consistency, conformity and control. It is the foundation of reliable brewing.

Colour scales in a table

Let us set the scales and example beer colours side by side:

The table shows how the colour scales correspond to beer styles. A pale lager is low values (2-4 SRM), an amber ale medium (9-14), a brown porter higher (20-30), and a black stout the highest (30-40 and more). EBC is roughly twice SRM. The higher the number, the darker the beer - because darker beer absorbs more light. It is an objective, numerical translation of colour into a value. Thanks to this breweries speak one language of colour. The SRM and EBC scales turn the impression of colour into a measurable value.

Why it is worth knowing this

Understanding the beer colour scales enriches the knowledge of beer. First, it shows that even colour, seemingly obvious, is the subject of precise measurement and science. Second, it explains how breweries know how to reproduce exactly the same shade of beer every time. Third, it helps understand beer descriptions and style guidelines, where colour is given in SRM or EBC. Fourth, for home brewers it is practical knowledge: you can calculate the colour of beer before brewing, choosing malts. Fifth, it shows the link between malt and colour: the colour of beer is a reflection of the malt used. A conscious beer lover knows that behind the colour of their favourite beer stands a malt recipe and a precise measurement. Next time, admiring the colour of beer in a glass, it is worth thinking about the scales that describe it. It is knowledge that deepens the understanding of beer and the appreciation of the craft of making it. The colour of beer is science hidden in a glass.

The key points in a nutshell

The colour of beer, coming mainly from the degree of malt kilning, is measured in three scales. Degrees Lovibond (from 1885, Joseph Lovibond) are the historical beginning, today used for malt. SRM (Standard Reference Method) is the American scale based on the measurement of light absorption, replacing subjective judgement. EBC (European Brewery Convention) is the European equivalent, where EBC equals about 1.97 times SRM (that is roughly twice). Colour from malt is calculated by the MCU method or the more accurate Morey equation. The darker the beer, the higher the number: a pale lager 2-4 SRM, a black stout 30-40+ SRM. Measurement gives repeatability, conformity with style and a common language. Want to compare beers of different colours and record your impressions? Keep tasting notes in the GustoNote app. See also our posts on dark beers and on beer numbers IBU, Plato and extract.