{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"srm-color"},"result":{"entity_type":"calculator","id":"srm-color","calculator_id":"srm-color","canonical_url":"https://tttkmbb.com/food/srm-color","name":"Beer Color (SRM) Calculator","title":"Beer Color Calculator – SRM, EBC and Lovibond from the Grain Bill (Morey Equation)","category":"food","category_name":"Food & Cooking","tool_name":"calculate_beer_color_srm","featured_mcp_tool":false,"description":"Predicts the colour of a beer from the grain bill: malt colour units (MCU) from grain weights, Lovibond ratings and batch volume, converted to SRM with the Morey equation, plus EBC, Lovibond, a descriptive colour name and an approximate hex colour.","use_when":"You are designing a beer recipe and want its predicted colour in SRM or EBC, or need to check whether a grain bill matches a style's colour range.","do_not_use_when":"The colour must be measured rather than predicted (SRM is defined by absorbance at 430 nm), or extract and adjunct colours are unknown; also unreliable above about 50 SRM where the Morey fit was not validated.","inputs":[{"name":"batch_volume","label":"Batch volume","type":"number","required":true,"max":100000,"exclusive_min":0,"description":"Final wort volume in volume_unit.","example":5},{"name":"volume_unit","label":"Volume unit","type":"enum","required":false,"default":"gal_us","values":[{"value":"gal_us","label":"US gallons","aliases":["gal","gallon","gallons","us gal"]},{"value":"l","label":"Litres","aliases":["liter","litre","liters","litres"]}],"description":"Unit of batch_volume.","example":"gal_us"},{"name":"grain_weights","label":"Grain weights","type":"number_list","required":true,"description":"Weight of each grain or extract in weight_unit, in order.","example":[10,1]},{"name":"weight_unit","label":"Weight unit","type":"enum","required":false,"default":"lb","values":[{"value":"lb","label":"Pounds","aliases":["lbs","pound","pounds"]},{"value":"kg","label":"Kilograms","aliases":["kilogram","kilograms","kilo","kilos"]}],"description":"Unit of grain_weights.","example":"lb"},{"name":"grain_colors_lovibond","label":"Grain colours","type":"number_list","unit":"°L","required":true,"description":"Colour rating of each grain in degrees Lovibond (from the maltster), same order as the weights.","example":[2,40]}],"outputs":[{"name":"mcu","label":"Malt colour units","type":"number","unit":"MCU","decimals":2,"description":"Σ(weight_lb × °L) / gallons."},{"name":"srm","label":"Colour (SRM)","type":"number","unit":"SRM","decimals":2,"description":"Standard Reference Method colour from the Morey equation."},{"name":"ebc","label":"Colour (EBC)","type":"number","unit":"EBC","decimals":1,"description":"European Brewery Convention colour = 1.97 × SRM."},{"name":"lovibond","label":"Colour (°Lovibond)","type":"number","unit":"°L","decimals":2,"description":"Approximate Lovibond value = (SRM + 0.76) / 1.3546."},{"name":"color_description","label":"Colour","type":"string","decimals":4,"description":"Descriptive colour name for the SRM band (pale straw to black)."},{"name":"hex_color_approx","label":"Hex colour (approx.)","type":"string","decimals":4,"description":"Approximate sRGB hex value for the nearest whole SRM (1–40) as used in homebrewing colour charts."}],"input_schema":{"type":"object","properties":{"batch_volume":{"description":"Final wort volume in volume_unit.","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[5]},"volume_unit":{"description":"Unit of batch_volume.","type":"string","enum":["gal_us","l"],"default":"gal_us","examples":["gal_us"]},"grain_weights":{"description":"Weight of each grain or extract in weight_unit, in order.","type":"array","items":{"type":"number"},"examples":[[10,1]]},"weight_unit":{"description":"Unit of grain_weights.","type":"string","enum":["lb","kg"],"default":"lb","examples":["lb"]},"grain_colors_lovibond":{"description":"Colour rating of each grain in degrees Lovibond (from the maltster), same order as the weights. Unit: °L.","type":"array","items":{"type":"number"},"examples":[[2,40]],"x-unit":"°L"}},"additionalProperties":false,"required":["batch_volume","grain_weights","grain_colors_lovibond"]},"output_schema":{"type":"object","properties":{"mcu":{"description":"Σ(weight_lb × °L) / gallons. Unit: MCU.","type":"number","x-unit":"MCU"},"srm":{"description":"Standard Reference Method colour from the Morey equation. Unit: SRM.","type":"number","x-unit":"SRM"},"ebc":{"description":"European Brewery Convention colour = 1.97 × SRM. Unit: EBC.","type":"number","x-unit":"EBC"},"lovibond":{"description":"Approximate Lovibond value = (SRM + 0.76) / 1.3546. Unit: °L.","type":"number","x-unit":"°L"},"color_description":{"description":"Descriptive colour name for the SRM band (pale straw to black).","type":"string"},"hex_color_approx":{"description":"Approximate sRGB hex value for the nearest whole SRM (1–40) as used in homebrewing colour charts.","type":"string"}}},"formula":"MCU = Σ(grain_weight_lb_i × grain_color_lovibond_i) / batch_volume_gal; SRM = 1.4922 × MCU^0.6859 (Morey); EBC = 1.97 × SRM; °L ≈ (SRM + 0.76) / 1.3546; 1 kg = 2.20462 lb, 1 US gal = 3.78541 L","method":"Morey's power-law fit reproduces measured colour better than the linear MCU value, which overestimates dark beers; it is considered reliable up to about 50 SRM. Colour names are approximate bands (2–3 pale straw, 3–4 straw, 4–6 pale gold, 6–9 gold, 9–12 amber, 12–15 copper, 15–18 red-brown, 18–22 brown, 22–30 dark brown, 30–35 black, above 35 opaque black).","sources":[{"name":"Wikipedia – Standard Reference Method (SRM, EBC and Lovibond beer colour scales)","url":"https://en.wikipedia.org/wiki/Standard_Reference_Method","type":"reference","retrieved_at":"2026-09-24"},{"name":"BJCP Style Guidelines (2021) – vital statistics for IBU, colour (SRM) and carbonation by style","url":"https://www.bjcp.org/bjcp-style-guidelines/","type":"standard","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Beer measurement (specific gravity, degrees Plato, IBU, SRM/EBC)","url":"https://en.wikipedia.org/wiki/Beer_measurement","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"5 gal: 10 lb at 2 °L + 1 lb at 40 °L","inputs":{"batch_volume":5,"volume_unit":"gal_us","grain_weights":[10,1],"weight_unit":"lb","grain_colors_lovibond":[2,40]},"expected":{"mcu":12,"srm":8.2,"ebc":16.2,"lovibond":6.62,"color_description":"Gold","hex_color_approx":"#EA8F00"},"url":"https://tttkmbb.com/api/v1/calculate/srm-color?batch_volume=5&volume_unit=gal_us&grain_weights=10%2C1&weight_unit=lb&grain_colors_lovibond=2%2C40"},{"name":"20 L: 4 kg at 3 °L, 0.5 kg at 120 °L, 0.25 kg at 500 °L","inputs":{"batch_volume":20,"volume_unit":"l","grain_weights":[4,0.5,0.25],"weight_unit":"kg","grain_colors_lovibond":[3,120,500]},"expected":{"mcu":82.2,"srm":30.71,"ebc":60.5,"color_description":"Black"},"url":"https://tttkmbb.com/api/v1/calculate/srm-color?batch_volume=20&volume_unit=l&grain_weights=4%2C0.5%2C0.25&weight_unit=kg&grain_colors_lovibond=3%2C120%2C500"}],"faq":[{"q":"Where do I find a grain's Lovibond rating?","a":"On the maltster's specification sheet; typical values are 1.5–3 °L for pale base malts, 10–120 °L for crystal malts and 300–600 °L for roasted malts. For EBC-rated European malts, °L ≈ (EBC / 1.97 + 0.76) / 1.3546."},{"q":"Why does the descriptive name differ from a style guide?","a":"Colour names are approximate bands; style guidelines such as the BJCP use their own slightly different band names, so compare the SRM number with the style's SRM range rather than the word."},{"q":"Does extract brewing change the calculation?","a":"No, but liquid and dry extracts have their own colour ratings (usually 2–4 °L for pale extract) and darken with long boils; use the manufacturer's value as the grain colour."}],"tags":["srm calculator","beer color","ebc calculator","lovibond","morey equation","malt color units"],"related":[{"calculator_id":"ibu-tinseth","reason":"Bitterness of the same recipe from the hop schedule."},{"calculator_id":"homebrew-abv","reason":"Alcohol content from gravity readings."},{"calculator_id":"volume","reason":"Convert batch volumes between gallons and litres."}],"links":{"html":"https://tttkmbb.com/food/srm-color","markdown":"https://tttkmbb.com/food/srm-color.md","json":"https://tttkmbb.com/food/srm-color.json","api":"https://tttkmbb.com/api/v1/calculate/srm-color","schema":"https://tttkmbb.com/api/v1/calculators/srm-color","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:47:23Z"}