{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"ibu-tinseth"},"result":{"entity_type":"calculator","id":"ibu-tinseth","calculator_id":"ibu-tinseth","canonical_url":"https://tttkmbb.com/food/ibu-tinseth","name":"IBU Calculator (Tinseth)","title":"IBU Calculator – Beer Bitterness from Hop Additions with the Tinseth Utilization Formula","category":"food","category_name":"Food & Cooking","tool_name":"calculate_ibu_tinseth","featured_mcp_tool":false,"description":"Computes the International Bitterness Units of a beer from up to 12 hop additions (weight, alpha-acid percentage, boil time) using Glenn Tinseth's utilization model, with a 10 % utilization bonus for pellet hops, and reports the BU:GU bitterness ratio.","use_when":"You are designing or checking a homebrew recipe and need the predicted IBU for a hop schedule at a given batch size and boil gravity.","do_not_use_when":"The bitterness comes from dry hopping, whirlpool or hop extracts (utilization models cover kettle additions only), or you need actual measured IBU (requires laboratory spectrophotometry).","inputs":[{"name":"batch_volume_l","label":"Batch volume","type":"number","unit":"L","required":true,"max":100000,"exclusive_min":0,"description":"Post-boil volume of wort in litres that the hops end up in (1 US gal = 3.785 L).","example":20},{"name":"boil_gravity","label":"Boil gravity","type":"number","unit":"SG","required":true,"min":1,"max":1.15,"description":"Average specific gravity of the wort during the boil; for a full-volume boil use the original gravity, for a concentrated boil the (higher) gravity of the kettle wort.","example":1.05},{"name":"hop_weights_g","label":"Hop weights","type":"number_list","unit":"g","required":true,"description":"Weight of each hop addition in grams (1 oz = 28.35 g), in order.","example":[30]},{"name":"alpha_acid_percents","label":"Alpha acid percentages","type":"number_list","unit":"%","required":true,"description":"Alpha-acid content of each addition in percent (from the packet), same order as the weights.","example":[10]},{"name":"boil_times_min","label":"Boil times","type":"number_list","unit":"min","required":true,"description":"Minutes each addition boils (0 for flame-out additions), same order.","example":[60]},{"name":"hop_form","label":"Hop form","type":"enum","required":false,"default":"whole","values":[{"value":"whole","label":"Whole / leaf hops","aliases":["leaf","cones","whole leaf"]},{"value":"pellet","label":"Pellet hops (+10 % utilization)","aliases":["pellets","t90"]}],"description":"Pellets release alpha acids more readily; the model multiplies utilization by 1.10 for pellets.","example":"whole"},{"name":"original_gravity","label":"Original gravity (for BU:GU)","type":"number","unit":"SG","required":false,"min":1,"max":1.2,"description":"Original gravity of the finished wort for the BU:GU ratio; defaults to boil_gravity.","example":1.05}],"outputs":[{"name":"total_ibu","label":"Total IBU","type":"number","unit":"IBU","decimals":1,"description":"Sum of the IBU of all additions (mg of isomerized alpha acids per litre)."},{"name":"additions","label":"Per addition","type":"list","decimals":2,"description":"Per hop addition: weight_g, alpha_acid_percent, boil_time_min, utilization_percent and ibu."},{"name":"bigness_factor","label":"Bigness factor","type":"number","decimals":4,"description":"Gravity term 1.65 × 0.000125^(boil_gravity − 1); higher gravity lowers utilization."},{"name":"bitterness_ratio","label":"BU:GU ratio","type":"number","decimals":2,"description":"total_ibu / ((original_gravity − 1) × 1000); below ≈ 0.3 reads malty, 0.3–0.6 balanced, above 0.6 hop-forward."},{"name":"style_note","label":"Bitterness level","type":"string","decimals":4,"description":"Descriptive bitterness level with typical styles at that IBU."}],"input_schema":{"type":"object","properties":{"batch_volume_l":{"description":"Post-boil volume of wort in litres that the hops end up in (1 US gal = 3.785 L). Unit: L.","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[20],"x-unit":"L"},"boil_gravity":{"description":"Average specific gravity of the wort during the boil; for a full-volume boil use the original gravity, for a concentrated boil the (higher) gravity of the kettle wort. Unit: SG.","type":"number","minimum":1,"maximum":1.15,"examples":[1.05],"x-unit":"SG"},"hop_weights_g":{"description":"Weight of each hop addition in grams (1 oz = 28.35 g), in order. Unit: g.","type":"array","items":{"type":"number"},"examples":[[30]],"x-unit":"g"},"alpha_acid_percents":{"description":"Alpha-acid content of each addition in percent (from the packet), same order as the weights. Unit: %.","type":"array","items":{"type":"number"},"examples":[[10]],"x-unit":"%"},"boil_times_min":{"description":"Minutes each addition boils (0 for flame-out additions), same order. Unit: min.","type":"array","items":{"type":"number"},"examples":[[60]],"x-unit":"min"},"hop_form":{"description":"Pellets release alpha acids more readily; the model multiplies utilization by 1.10 for pellets.","type":"string","enum":["whole","pellet"],"default":"whole","examples":["whole"]},"original_gravity":{"description":"Original gravity of the finished wort for the BU:GU ratio; defaults to boil_gravity. Unit: SG.","type":"number","minimum":1,"maximum":1.2,"examples":[1.05],"x-unit":"SG"}},"additionalProperties":false,"required":["batch_volume_l","boil_gravity","hop_weights_g","alpha_acid_percents","boil_times_min"]},"output_schema":{"type":"object","properties":{"total_ibu":{"description":"Sum of the IBU of all additions (mg of isomerized alpha acids per litre). Unit: IBU.","type":"number","x-unit":"IBU"},"additions":{"description":"Per hop addition: weight_g, alpha_acid_percent, boil_time_min, utilization_percent and ibu.","type":"array"},"bigness_factor":{"description":"Gravity term 1.65 × 0.000125^(boil_gravity − 1); higher gravity lowers utilization.","type":"number"},"bitterness_ratio":{"description":"total_ibu / ((original_gravity − 1) × 1000); below ≈ 0.3 reads malty, 0.3–0.6 balanced, above 0.6 hop-forward.","type":"number"},"style_note":{"description":"Descriptive bitterness level with typical styles at that IBU.","type":"string"}}},"formula":"U_i = 1.65 × 0.000125^(boil_gravity − 1) × (1 − e^(−0.04 × boil_time_i)) / 4.15 (× 1.10 for pellets); IBU_i = hop_weight_g_i × alpha_acid_percent_i / 100 × U_i × 1000 / batch_volume_l; total_ibu = Σ IBU_i; BU:GU = total_ibu / ((original_gravity − 1) × 1000)","method":"Tinseth's utilization model (1997) was fitted to measured homebrew batches and is the one used by most recipe software; real utilization varies with kettle geometry, hop age and wort pH, and predictions above about 100 IBU exceed what can be measured. The 10 % pellet adjustment is common practice rather than part of the original model.","sources":[{"name":"Palmer, J. – How to Brew (online 1st ed.), Hop bittering calculations (Tinseth utilization model)","url":"https://www.howtobrew.com/book/section-1/hops/hop-bittering-calculations","type":"textbook","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":"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"}],"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":"20 L, 1.050, 30 g whole hops at 10 % for 60 min","inputs":{"batch_volume_l":20,"boil_gravity":1.05,"hop_weights_g":[30],"alpha_acid_percents":[10],"boil_times_min":[60],"hop_form":"whole"},"expected":{"total_ibu":34.6,"bigness_factor":1.0528,"additions":[{"weight_g":30,"alpha_acid_percent":10,"boil_time_min":60,"utilization_percent":23.07,"ibu":34.6}],"bitterness_ratio":0.69},"url":"https://tttkmbb.com/api/v1/calculate/ibu-tinseth?batch_volume_l=20&boil_gravity=1.05&hop_weights_g=30&alpha_acid_percents=10&boil_times_min=60&hop_form=whole"},{"name":"23 L, 1.060, three pellet additions","inputs":{"batch_volume_l":23,"boil_gravity":1.06,"hop_weights_g":[40,25,30],"alpha_acid_percents":[6.5,5.5,5.5],"boil_times_min":[60,15,5],"hop_form":"pellet","original_gravity":1.06},"expected":{"total_ibu":36.4,"additions":[{"ibu":26.22},{"ibu":6.88},{"ibu":3.32}],"bitterness_ratio":0.61},"url":"https://tttkmbb.com/api/v1/calculate/ibu-tinseth?batch_volume_l=23&boil_gravity=1.06&hop_weights_g=40%2C25%2C30&alpha_acid_percents=6.5%2C5.5%2C5.5&boil_times_min=60%2C15%2C5&hop_form=pellet&original_gravity=1.06"}],"faq":[{"q":"Which gravity do I enter for boil_gravity?","a":"The average gravity of the wort while the hops are boiling. For a full-volume boil that is close to the original gravity; for a partial boil topped up with water afterwards, use the kettle gravity, which is higher and lowers utilization."},{"q":"Why do other calculators (Rager, Garetz) give different IBU?","a":"Each model was fitted to different data; Rager predicts 10–30 % more IBU than Tinseth for long boils. Always compare recipes using the same model."},{"q":"How do I count whirlpool or flame-out hops?","a":"Enter 0 minutes and they contribute nothing here, although hot-side steeping does add some bitterness; some brewers enter 5–10 minutes as a rough proxy."}],"tags":["ibu calculator","tinseth","hop utilization","beer bitterness","bu gu ratio","homebrew hops"],"related":[{"calculator_id":"homebrew-abv","reason":"Alcohol content of the same recipe from gravity readings."},{"calculator_id":"srm-color","reason":"Predict the beer colour from the grain bill."},{"calculator_id":"mass","reason":"Convert hop weights between ounces and grams."}],"links":{"html":"https://tttkmbb.com/food/ibu-tinseth","markdown":"https://tttkmbb.com/food/ibu-tinseth.md","json":"https://tttkmbb.com/food/ibu-tinseth.json","api":"https://tttkmbb.com/api/v1/calculate/ibu-tinseth","schema":"https://tttkmbb.com/api/v1/calculators/ibu-tinseth","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:50:01Z","next_actions":[{"tool":"run_calculator","calculator_id":"ibu-tinseth","reason":"Run IBU Calculator (Tinseth) with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/food/ibu-tinseth.md"}}