{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"homebrew-abv"},"result":{"entity_type":"calculator","id":"homebrew-abv","calculator_id":"homebrew-abv","canonical_url":"https://tttkmbb.com/food/homebrew-abv","name":"Homebrew ABV Calculator","title":"Homebrew ABV Calculator – Alcohol, Attenuation, Plato and Calories from Original and Final Gravity","category":"food","category_name":"Food & Cooking","tool_name":"calculate_homebrew_abv","featured_mcp_tool":false,"description":"Computes a beer's alcohol by volume from original and final specific gravity with the standard (OG − FG) × 131.25 formula and the alternate high-gravity formula, plus alcohol by weight, apparent attenuation, degrees Plato, real extract and calories per serving.","use_when":"You have hydrometer readings (or refractometer readings corrected for alcohol) before and after fermentation and want the alcohol content, attenuation or calorie content of a homebrewed beer, cider or mead.","do_not_use_when":"You need the strength of a mixed drink (use cocktail-abv) or the readings come from an uncorrected refractometer after fermentation (alcohol distorts Brix readings). Results are informational and must not be used to decide whether someone is fit to drive.","inputs":[{"name":"original_gravity","label":"Original gravity (OG)","type":"number","unit":"SG","required":true,"min":1.001,"max":1.2,"description":"Specific gravity of the wort or must before fermentation, e.g. 1.050.","example":1.05},{"name":"final_gravity","label":"Final gravity (FG)","type":"number","unit":"SG","required":true,"min":0.98,"max":1.1,"description":"Specific gravity after fermentation, e.g. 1.010; must be lower than the original gravity.","example":1.01}],"outputs":[{"name":"abv_standard_percent","label":"ABV (standard formula)","type":"number","unit":"%","decimals":2,"description":"Alcohol by volume = (OG − FG) × 131.25."},{"name":"abv_alternate_percent","label":"ABV (alternate formula)","type":"number","unit":"%","decimals":2,"description":"Alcohol by volume from the non-linear formula 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794, more accurate above about 6–7 % ABV."},{"name":"abw_percent","label":"Alcohol by weight","type":"number","unit":"%","decimals":2,"description":"ABW = ABV × 0.789 / FG (ethanol density 0.789 g/ml relative to the beer's density)."},{"name":"apparent_attenuation_percent","label":"Apparent attenuation","type":"number","unit":"%","decimals":1,"description":"(OG − FG) / (OG − 1) × 100; typical ale and lager yeasts reach 65–85 %."},{"name":"original_plato","label":"Original extract","type":"number","unit":"°P","decimals":2,"description":"Original gravity converted to degrees Plato (cubic SG→°P fit)."},{"name":"final_plato","label":"Apparent final extract","type":"number","unit":"°P","decimals":2,"description":"Final gravity converted to degrees Plato (apparent extract)."},{"name":"real_extract_plato","label":"Real extract","type":"number","unit":"°P","decimals":2,"description":"Balling: 0.1808 × original °P + 0.8192 × apparent final °P (residual sugars after correcting for the lighter alcohol)."},{"name":"real_attenuation_percent","label":"Real attenuation","type":"number","unit":"%","decimals":1,"description":"(original °P − real extract) / original °P × 100."},{"name":"calories_per_12oz","label":"Calories per 12 US fl oz","type":"number","unit":"kcal","decimals":0,"description":"Energy from alcohol and residual extract in a 355 ml serving."},{"name":"calories_per_100ml","label":"Calories per 100 ml","type":"number","unit":"kcal","decimals":1,"description":"Same energy expressed per 100 ml (12 US fl oz = 354.88 ml)."}],"input_schema":{"type":"object","properties":{"original_gravity":{"description":"Specific gravity of the wort or must before fermentation, e.g. 1.050. Unit: SG.","type":"number","minimum":1.001,"maximum":1.2,"examples":[1.05],"x-unit":"SG"},"final_gravity":{"description":"Specific gravity after fermentation, e.g. 1.010; must be lower than the original gravity. Unit: SG.","type":"number","minimum":0.98,"maximum":1.1,"examples":[1.01],"x-unit":"SG"}},"additionalProperties":false,"required":["original_gravity","final_gravity"]},"output_schema":{"type":"object","properties":{"abv_standard_percent":{"description":"Alcohol by volume = (OG − FG) × 131.25. Unit: %.","type":"number","x-unit":"%"},"abv_alternate_percent":{"description":"Alcohol by volume from the non-linear formula 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794, more accurate above about 6–7 % ABV. Unit: %.","type":"number","x-unit":"%"},"abw_percent":{"description":"ABW = ABV × 0.789 / FG (ethanol density 0.789 g/ml relative to the beer's density). Unit: %.","type":"number","x-unit":"%"},"apparent_attenuation_percent":{"description":"(OG − FG) / (OG − 1) × 100; typical ale and lager yeasts reach 65–85 %. Unit: %.","type":"number","x-unit":"%"},"original_plato":{"description":"Original gravity converted to degrees Plato (cubic SG→°P fit). Unit: °P.","type":"number","x-unit":"°P"},"final_plato":{"description":"Final gravity converted to degrees Plato (apparent extract). Unit: °P.","type":"number","x-unit":"°P"},"real_extract_plato":{"description":"Balling: 0.1808 × original °P + 0.8192 × apparent final °P (residual sugars after correcting for the lighter alcohol). Unit: °P.","type":"number","x-unit":"°P"},"real_attenuation_percent":{"description":"(original °P − real extract) / original °P × 100. Unit: %.","type":"number","x-unit":"%"},"calories_per_12oz":{"description":"Energy from alcohol and residual extract in a 355 ml serving. Unit: kcal.","type":"number","x-unit":"kcal"},"calories_per_100ml":{"description":"Same energy expressed per 100 ml (12 US fl oz = 354.88 ml). Unit: kcal.","type":"number","x-unit":"kcal"}}},"formula":"ABV = (OG − FG) × 131.25; ABV_alt = 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794; ABW = ABV × 0.789 / FG; apparent attenuation = (OG − FG) / (OG − 1) × 100; °P = −616.868 + 1111.14·SG − 630.272·SG² + 135.997·SG³; real extract = 0.1808·OP + 0.8192·AP; real attenuation = (OP − RE) / OP × 100; kcal per 12 oz = 1881.22·FG·(OG − FG) / (1.775 − OG) + 3550·FG·(0.1808·OG + 0.8114·FG − 1); kcal per 100 ml = kcal per 12 oz / 3.5488","method":"The 131.25 factor is accurate to about ±0.5 % ABV for beers up to roughly 7 %; the alternate formula corrects for the non-linear relation between gravity drop and alcohol at higher gravities. The calorie formula (alcohol plus residual extract) is the one used by homebrewing references and does not account for unfermentable additions. Informational only: results must not be used to decide whether anyone is fit to drive.","sources":[{"name":"Wikipedia – Alcohol by volume (ABV from gravity difference; ABV/ABW relation)","url":"https://en.wikipedia.org/wiki/Alcohol_by_volume","type":"reference","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"},{"name":"Brewer's Friend – ABV calculator (standard and alternate ABV formulas, calorie formula)","url":"https://www.brewersfriend.com/abv-calculator/","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":"OG 1.050, FG 1.010","inputs":{"original_gravity":1.05,"final_gravity":1.01},"expected":{"abv_standard_percent":5.25,"abv_alternate_percent":5.34,"apparent_attenuation_percent":80,"original_plato":12.39,"final_plato":2.56,"calories_per_12oz":138},"url":"https://tttkmbb.com/api/v1/calculate/homebrew-abv?original_gravity=1.05&final_gravity=1.01"},{"name":"OG 1.080, FG 1.020 (strong ale)","inputs":{"original_gravity":1.08,"final_gravity":1.02},"expected":{"abv_standard_percent":7.88,"abv_alternate_percent":8.44,"apparent_attenuation_percent":75,"original_plato":19.33,"calories_per_12oz":249},"url":"https://tttkmbb.com/api/v1/calculate/homebrew-abv?original_gravity=1.08&final_gravity=1.02"}],"faq":[{"q":"Which ABV formula should I report?","a":"Use the standard formula for ordinary beers; it is what most competitions and recipe software use. Above about 1.070 OG the alternate formula is closer to laboratory values because the simple linear factor under-reads."},{"q":"Do I need to temperature-correct my hydrometer readings?","a":"Yes: most hydrometers are calibrated at 15.6 or 20 °C. Take both readings at the calibration temperature or apply the same correction to each before entering them."},{"q":"Why does the final gravity read below 1.000 sometimes?","a":"Alcohol is lighter than water, so a very dry beer, cider or mead can finish at 0.990–0.998; the calculator accepts final gravities down to 0.980."}],"tags":["abv calculator","homebrew alcohol content","original gravity final gravity","attenuation","beer calories","plato conversion"],"related":[{"calculator_id":"priming-sugar","reason":"Bottle-condition the finished beer to a target carbonation."},{"calculator_id":"ibu-tinseth","reason":"Bitterness of the same recipe from the hop additions."},{"calculator_id":"cocktail-abv","reason":"Alcohol content of mixed drinks."}],"links":{"html":"https://tttkmbb.com/food/homebrew-abv","markdown":"https://tttkmbb.com/food/homebrew-abv.md","json":"https://tttkmbb.com/food/homebrew-abv.json","api":"https://tttkmbb.com/api/v1/calculate/homebrew-abv","schema":"https://tttkmbb.com/api/v1/calculators/homebrew-abv","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:50:06Z"}