{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"one-rep-max"},"result":{"entity_type":"calculator","id":"one-rep-max","calculator_id":"one-rep-max","canonical_url":"https://tttkmbb.com/fitness/one-rep-max","name":"One-Rep Max Calculator","title":"One-Rep Max (1RM) Calculator – Epley, Brzycki and Lombardi Estimates with Percentage Table","category":"fitness","category_name":"Sports & Fitness","tool_name":"estimate_one_rep_max","featured_mcp_tool":false,"description":"Estimates the one-repetition maximum from a weight lifted for 2–12 repetitions using the Epley, Brzycki and Lombardi equations, reports their average, and lists training loads at 95 % to 70 % of that 1RM.","use_when":"You want to estimate maximal strength or program training percentages without attempting a true single-rep maximum.","do_not_use_when":"The set was more than 12 repetitions (prediction error grows quickly) or was not taken close to failure; use a heavier, lower-rep set instead.","inputs":[{"name":"weight_lifted","label":"Weight lifted","type":"number","unit":"kg or lb","required":true,"max":2000,"exclusive_min":0,"description":"Load lifted for the set, in any unit; outputs use the same unit.","example":100},{"name":"reps","label":"Repetitions","type":"integer","unit":"reps","required":true,"min":2,"max":12,"description":"Repetitions completed with that load, ideally to (near) failure.","example":5}],"outputs":[{"name":"one_rep_max","label":"Estimated 1RM (average)","type":"number","decimals":1,"description":"Mean of the Epley, Brzycki and Lombardi estimates, in the unit of weight_lifted."},{"name":"epley","label":"Epley","type":"number","decimals":1,"description":"1RM = w × (1 + reps / 30)."},{"name":"brzycki","label":"Brzycki","type":"number","decimals":1,"description":"1RM = w × 36 / (37 − reps)."},{"name":"lombardi","label":"Lombardi","type":"number","decimals":1,"description":"1RM = w × reps^0.10."},{"name":"percentages","label":"Training loads","type":"list","decimals":1,"description":"Load at 95, 90, 85, 80, 75 and 70 % of the averaged 1RM."}],"input_schema":{"type":"object","properties":{"weight_lifted":{"description":"Load lifted for the set, in any unit; outputs use the same unit. Unit: kg or lb.","type":"number","maximum":2000,"exclusiveMinimum":0,"examples":[100],"x-unit":"kg or lb"},"reps":{"description":"Repetitions completed with that load, ideally to (near) failure. Unit: reps.","type":"integer","minimum":2,"maximum":12,"examples":[5],"x-unit":"reps"}},"additionalProperties":false,"required":["weight_lifted","reps"]},"output_schema":{"type":"object","properties":{"one_rep_max":{"description":"Mean of the Epley, Brzycki and Lombardi estimates, in the unit of weight_lifted.","type":"number"},"epley":{"description":"1RM = w × (1 + reps / 30).","type":"number"},"brzycki":{"description":"1RM = w × 36 / (37 − reps).","type":"number"},"lombardi":{"description":"1RM = w × reps^0.10.","type":"number"},"percentages":{"description":"Load at 95, 90, 85, 80, 75 and 70 % of the averaged 1RM.","type":"array"}}},"formula":"Epley: 1RM = w × (1 + reps/30); Brzycki: 1RM = w × 36 / (37 − reps); Lombardi: 1RM = w × reps^0.10; one_rep_max = (Epley + Brzycki + Lombardi) / 3; load_p = one_rep_max × p / 100","method":"The equations agree within about 2 % for 2–6 reps and Epley and Brzycki coincide at 10 reps; beyond that Brzycki rises fastest and Lombardi stays lowest, so estimates diverge. Percentages use the averaged estimate.","sources":[{"name":"Reynolds JM, Gordon TJ, Robergs RA (2006) Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry, J Strength Cond Res 20:584-592","url":"https://pubmed.ncbi.nlm.nih.gov/16937972/","type":"peer_reviewed","retrieved_at":"2026-09-24"},{"name":"Wikipedia – One-repetition maximum (formula collection with original citations: Epley 1985, Brzycki 1993, Lombardi 1989)","url":"https://en.wikipedia.org/wiki/One-repetition_maximum","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":"100 kg × 5 reps","inputs":{"weight_lifted":100,"reps":5},"expected":{"epley":116.7,"brzycki":112.5,"lombardi":117.5,"one_rep_max":115.5,"percentages":[{"percent":95,"load":109.8},{"percent":90,"load":104},{"percent":85,"load":98.2},{"percent":80,"load":92.4},{"percent":75,"load":86.7},{"percent":70,"load":80.9}]},"url":"https://tttkmbb.com/api/v1/calculate/one-rep-max?weight_lifted=100&reps=5"},{"name":"60 kg × 10 reps","inputs":{"weight_lifted":60,"reps":10},"expected":{"epley":80,"brzycki":80,"lombardi":75.5,"one_rep_max":78.5},"url":"https://tttkmbb.com/api/v1/calculate/one-rep-max?weight_lifted=60&reps=10"}],"faq":[{"q":"Which formula is best?","a":"For 2–6 reps they agree closely; Brzycki is widely used in the USA for bench press, Epley for squat and deadlift. Averaging reduces the influence of any one equation's bias."},{"q":"Can I use pounds?","a":"Yes. The equations are unit-free: enter pounds and every output is in pounds."}],"tags":["one rep max","1rm calculator","epley","brzycki","lombardi","strength training percentages"],"related":[{"calculator_id":"protein-intake","reason":"Protein targets for strength and muscle gain."},{"calculator_id":"calories-burned","reason":"Energy cost of a weight-training session."}],"links":{"html":"https://tttkmbb.com/fitness/one-rep-max","markdown":"https://tttkmbb.com/fitness/one-rep-max.md","json":"https://tttkmbb.com/fitness/one-rep-max.json","api":"https://tttkmbb.com/api/v1/calculate/one-rep-max","schema":"https://tttkmbb.com/api/v1/calculators/one-rep-max","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-23T23:33:21Z","next_actions":[{"tool":"run_calculator","calculator_id":"one-rep-max","reason":"Run One-Rep Max Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/fitness/one-rep-max.md"}}