{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"bac-widmark"},"result":{"entity_type":"calculator","id":"bac-widmark","calculator_id":"bac-widmark","canonical_url":"https://tttkmbb.com/health/bac-widmark","name":"Blood Alcohol Content Calculator","title":"Blood Alcohol Content (BAC) Calculator – Widmark Formula with Elimination Over Time","category":"health","category_name":"Health","tool_name":"estimate_blood_alcohol_widmark","featured_mcp_tool":false,"description":"Estimates blood alcohol concentration from body weight, sex, number of standard drinks and hours since drinking started with the Widmark formula (Widmark 1932), reported in %, g/L and mg/100 mL together with the peak value and the hours until the estimate returns to zero.","use_when":"You need a rough BAC estimate for a known number of drinks and elapsed time, the peak BAC before elimination, or how long until the estimate reaches zero.","do_not_use_when":"You need to decide whether someone can drive or is legally intoxicated: the result is informational only, not medical or legal advice, and real BAC varies widely between people; to count drinks or grams of alcohol first, use standard-drinks.","inputs":[{"name":"weight_kg","label":"Body weight","type":"number","unit":"kg","required":true,"min":20,"max":400,"description":"Body weight in kilograms.","example":80},{"name":"sex","label":"Biological sex","type":"enum","required":true,"values":[{"value":"male","label":"Male (Widmark r = 0.68)","aliases":["m","man"]},{"value":"female","label":"Female (Widmark r = 0.55)","aliases":["f","woman"]}],"description":"Selects the Widmark distribution ratio r: 0.68 for men, 0.55 for women (average body-water fractions).","example":"male"},{"name":"standard_drinks","label":"Standard drinks","type":"number","required":true,"min":0,"max":60,"description":"Number of standard drinks consumed since the first drink.","example":4},{"name":"grams_alcohol_per_drink","label":"Alcohol per standard drink","type":"number","unit":"g","required":false,"default":14,"min":1,"max":50,"description":"Grams of pure ethanol in one standard drink: 14 g in the US (NIAAA), 10 g in Australia and much of Europe, 8 g for a UK unit.","example":14},{"name":"hours_since_first_drink","label":"Hours since first drink","type":"number","unit":"h","required":true,"min":0,"max":48,"description":"Time elapsed since drinking started.","example":2},{"name":"elimination_rate_percent_per_hour","label":"Elimination rate","type":"number","unit":"%/h","required":false,"default":0.015,"min":0.008,"max":0.03,"description":"BAC eliminated per hour (Widmark β). Typical adults eliminate 0.010–0.020 %/h; 0.015 is the usual average.","example":0.015}],"outputs":[{"name":"bac_percent","label":"Estimated BAC","type":"number","unit":"%","decimals":3,"description":"Blood alcohol concentration now, in grams per 100 mL of blood (% w/v), floored at 0."},{"name":"bac_g_per_l","label":"BAC (g/L)","type":"number","unit":"g/L","decimals":3,"description":"Same value in grams per litre (‰), the unit used in most of continental Europe."},{"name":"bac_mg_per_100ml","label":"BAC (mg/100 mL)","type":"number","unit":"mg/100 mL","decimals":1,"description":"Same value in milligrams per 100 mL, the unit used in the UK and Ireland."},{"name":"peak_bac_percent","label":"Peak BAC (before elimination)","type":"number","unit":"%","decimals":3,"description":"Widmark BAC if all alcohol were absorbed at once, before any elimination."},{"name":"hours_to_zero","label":"Hours until zero","type":"number","unit":"h","decimals":2,"description":"Time from now until the estimate reaches 0: bac_percent / elimination rate."},{"name":"interpretation","label":"Interpretation","type":"string","decimals":4,"description":"Typical-effects band for the estimated BAC (< 0.02, 0.02–0.05, 0.05–0.08, ≥ 0.08 %); legal driving limits vary by country."},{"name":"warning","label":"Warning","type":"string","decimals":4,"description":"Fixed safety warning returned with every result."}],"input_schema":{"type":"object","properties":{"weight_kg":{"description":"Body weight in kilograms. Unit: kg.","type":"number","minimum":20,"maximum":400,"examples":[80],"x-unit":"kg"},"sex":{"description":"Selects the Widmark distribution ratio r: 0.68 for men, 0.55 for women (average body-water fractions).","type":"string","enum":["male","female"],"examples":["male"]},"standard_drinks":{"description":"Number of standard drinks consumed since the first drink.","type":"number","minimum":0,"maximum":60,"examples":[4]},"grams_alcohol_per_drink":{"description":"Grams of pure ethanol in one standard drink: 14 g in the US (NIAAA), 10 g in Australia and much of Europe, 8 g for a UK unit. Unit: g.","type":"number","minimum":1,"maximum":50,"default":14,"examples":[14],"x-unit":"g"},"hours_since_first_drink":{"description":"Time elapsed since drinking started. Unit: h.","type":"number","minimum":0,"maximum":48,"examples":[2],"x-unit":"h"},"elimination_rate_percent_per_hour":{"description":"BAC eliminated per hour (Widmark β). Typical adults eliminate 0.010–0.020 %/h; 0.015 is the usual average. Unit: %/h.","type":"number","minimum":0.008,"maximum":0.03,"default":0.015,"examples":[0.015],"x-unit":"%/h"}},"additionalProperties":false,"required":["weight_kg","sex","standard_drinks","hours_since_first_drink"]},"output_schema":{"type":"object","properties":{"bac_percent":{"description":"Blood alcohol concentration now, in grams per 100 mL of blood (% w/v), floored at 0. Unit: %.","type":"number","x-unit":"%"},"bac_g_per_l":{"description":"Same value in grams per litre (‰), the unit used in most of continental Europe. Unit: g/L.","type":"number","x-unit":"g/L"},"bac_mg_per_100ml":{"description":"Same value in milligrams per 100 mL, the unit used in the UK and Ireland. Unit: mg/100 mL.","type":"number","x-unit":"mg/100 mL"},"peak_bac_percent":{"description":"Widmark BAC if all alcohol were absorbed at once, before any elimination. Unit: %.","type":"number","x-unit":"%"},"hours_to_zero":{"description":"Time from now until the estimate reaches 0: bac_percent / elimination rate. Unit: h.","type":"number","x-unit":"h"},"interpretation":{"description":"Typical-effects band for the estimated BAC (< 0.02, 0.02–0.05, 0.05–0.08, ≥ 0.08 %); legal driving limits vary by country.","type":"string"},"warning":{"description":"Fixed safety warning returned with every result.","type":"string"}}},"formula":"peak_bac_percent = standard_drinks × grams_alcohol_per_drink / (r × weight_kg × 1000) × 100 with r = 0.68 (male) or 0.55 (female); bac_percent = max(0, peak_bac_percent − elimination_rate_percent_per_hour × hours_since_first_drink); bac_g_per_l = bac_percent × 10; bac_mg_per_100ml = bac_percent × 1000; hours_to_zero = bac_percent / elimination_rate_percent_per_hour","method":"Widmark's formula assumes instantaneous absorption and constant (zero-order) elimination; food, drinking pace, body composition, medication and genetics change real BAC by ±0.02 % or more. Informational only, not medical or legal advice; never use it to decide whether to drive.","sources":[{"name":"Wikipedia – Blood alcohol content (Widmark formula)","url":"https://en.wikipedia.org/wiki/Blood_alcohol_content","type":"reference","retrieved_at":"2026-09-24"},{"name":"NIAAA – What Is a Standard Drink?","url":"https://www.niaaa.nih.gov/alcohols-effects-health/overview-alcohol-consumption/what-standard-drink","type":"government","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":"80 kg male, 4 US drinks, 2 h","inputs":{"weight_kg":80,"sex":"male","standard_drinks":4,"grams_alcohol_per_drink":14,"hours_since_first_drink":2},"expected":{"peak_bac_percent":0.103,"bac_percent":0.073,"bac_g_per_l":0.729,"bac_mg_per_100ml":72.9,"hours_to_zero":4.86},"url":"https://tttkmbb.com/api/v1/calculate/bac-widmark?weight_kg=80&sex=male&standard_drinks=4&grams_alcohol_per_drink=14&hours_since_first_drink=2"},{"name":"60 kg female, 2 Australian drinks (10 g), 1 h","inputs":{"weight_kg":60,"sex":"female","standard_drinks":2,"grams_alcohol_per_drink":10,"hours_since_first_drink":1},"expected":{"peak_bac_percent":0.061,"bac_percent":0.046,"hours_to_zero":3.04},"url":"https://tttkmbb.com/api/v1/calculate/bac-widmark?weight_kg=60&sex=female&standard_drinks=2&grams_alcohol_per_drink=10&hours_since_first_drink=1"}],"faq":[{"q":"Why does the estimate differ from a breathalyser?","a":"Widmark uses population-average water fractions and elimination rates and ignores absorption time and food. Individual results commonly deviate by ±0.02 % BAC or more, which is why it must not be used for driving decisions."},{"q":"How do I convert between %, g/L and mg/100 mL?","a":"0.05 % = 0.5 g/L (0.5 ‰) = 50 mg/100 mL. Multiply percent by 10 for g/L and by 1000 for mg/100 mL."},{"q":"Which grams-per-drink value should I use?","a":"14 g for a US standard drink (12 oz 5 % beer, 5 oz 12 % wine, 1.5 oz 40 % spirits), 10 g for Australian, WHO and most European standard drinks, 8 g for a UK unit. Use standard-drinks to convert a specific beverage."}],"tags":["bac","blood alcohol content","widmark formula","blood alcohol calculator","alcohol elimination"],"related":[{"calculator_id":"standard-drinks","reason":"Convert a beverage's volume and ABV into standard drinks and grams of alcohol to enter here."}],"links":{"html":"https://tttkmbb.com/health/bac-widmark","markdown":"https://tttkmbb.com/health/bac-widmark.md","json":"https://tttkmbb.com/health/bac-widmark.json","api":"https://tttkmbb.com/api/v1/calculate/bac-widmark","schema":"https://tttkmbb.com/api/v1/calculators/bac-widmark","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:44:38Z","next_actions":[{"tool":"run_calculator","calculator_id":"bac-widmark","reason":"Run Blood Alcohol Content Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/health/bac-widmark.md"}}