{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"sweat-rate"},"result":{"entity_type":"calculator","id":"sweat-rate","calculator_id":"sweat-rate","canonical_url":"https://tttkmbb.com/fitness/sweat-rate","name":"Sweat Rate Calculator","title":"Sweat Rate Calculator – Fluid Loss per Hour from Pre- and Post-Exercise Weight (ACSM Method)","category":"fitness","category_name":"Sports & Fitness","tool_name":"calculate_sweat_rate","featured_mcp_tool":false,"description":"Calculates sweat loss and sweat rate from body weight before and after exercise, corrected for fluid drunk and urine passed, plus the percentage of body mass lost, a dehydration classification and the volume to drink afterwards (150 % of the deficit), following the ACSM position stand on exercise and fluid replacement.","use_when":"An athlete weighed themselves before and after a session and wants their sweat rate, how dehydrated they became, or how much to drink during and after similar sessions.","do_not_use_when":"You want general daily fluid needs (use water-intake), the weights were taken with wet clothing or after eating, or for clinical dehydration assessment; results are informational, not medical advice.","inputs":[{"name":"pre_exercise_weight_kg","label":"Weight before","type":"number","unit":"kg","required":true,"max":300,"exclusive_min":0,"description":"Nude (or minimal dry clothing) body weight before exercise, after emptying the bladder.","example":70},{"name":"post_exercise_weight_kg","label":"Weight after","type":"number","unit":"kg","required":true,"max":300,"exclusive_min":0,"description":"Body weight after exercise, towelled dry, same clothing and scale.","example":69.2},{"name":"fluid_intake_ml","label":"Fluid drunk","type":"number","unit":"mL","required":false,"default":0,"min":0,"max":10000,"description":"Volume of fluid consumed during the session.","example":500},{"name":"urine_output_ml","label":"Urine passed","type":"number","unit":"mL","required":false,"default":0,"min":0,"max":5000,"description":"Urine volume passed between the two weighings (0 if none).","example":0},{"name":"duration_minutes","label":"Duration","type":"number","unit":"min","required":true,"max":1440,"exclusive_min":0,"description":"Exercise duration between the two weighings.","example":60}],"outputs":[{"name":"sweat_loss_liters","label":"Sweat loss","type":"number","unit":"L","decimals":2,"description":"(pre − post) + fluid drunk − urine, in litres (1 kg of body mass ≈ 1 L)."},{"name":"sweat_rate_l_per_hour","label":"Sweat rate","type":"number","unit":"L/h","decimals":2,"description":"Sweat loss divided by the duration in hours."},{"name":"sweat_rate_ml_per_hour","label":"Sweat rate","type":"number","unit":"mL/h","decimals":0,"description":"The same rate in millilitres per hour."},{"name":"body_mass_loss_percent","label":"Body mass loss","type":"number","unit":"%","decimals":2,"description":"(pre − post) / pre × 100; negative when weight was gained."},{"name":"dehydration_status","label":"Dehydration status","type":"string","decimals":4,"description":"< 2 % minimal; 2–3 % performance impaired; > 3 % significant (ACSM thresholds)."},{"name":"fluid_to_replace_ml","label":"Fluid to drink for recovery","type":"number","unit":"mL","decimals":0,"description":"150 % of the net body-mass deficit, drunk over the hours after exercise (ACSM)."},{"name":"recommended_intake_ml_per_hour_next_session","label":"Intake for the next session","type":"number","unit":"mL/h","decimals":0,"description":"Hourly intake that would match the sweat rate in the same conditions (an upper bound: ACSM advises keeping the loss below 2 % of body mass without drinking more than you sweat)."}],"input_schema":{"type":"object","properties":{"pre_exercise_weight_kg":{"description":"Nude (or minimal dry clothing) body weight before exercise, after emptying the bladder. Unit: kg.","type":"number","maximum":300,"exclusiveMinimum":0,"examples":[70],"x-unit":"kg"},"post_exercise_weight_kg":{"description":"Body weight after exercise, towelled dry, same clothing and scale. Unit: kg.","type":"number","maximum":300,"exclusiveMinimum":0,"examples":[69.2],"x-unit":"kg"},"fluid_intake_ml":{"description":"Volume of fluid consumed during the session. Unit: mL.","type":"number","minimum":0,"maximum":10000,"default":0,"examples":[500],"x-unit":"mL"},"urine_output_ml":{"description":"Urine volume passed between the two weighings (0 if none). Unit: mL.","type":"number","minimum":0,"maximum":5000,"default":0,"examples":[0],"x-unit":"mL"},"duration_minutes":{"description":"Exercise duration between the two weighings. Unit: min.","type":"number","maximum":1440,"exclusiveMinimum":0,"examples":[60],"x-unit":"min"}},"additionalProperties":false,"required":["pre_exercise_weight_kg","post_exercise_weight_kg","duration_minutes"]},"output_schema":{"type":"object","properties":{"sweat_loss_liters":{"description":"(pre − post) + fluid drunk − urine, in litres (1 kg of body mass ≈ 1 L). Unit: L.","type":"number","x-unit":"L"},"sweat_rate_l_per_hour":{"description":"Sweat loss divided by the duration in hours. Unit: L/h.","type":"number","x-unit":"L/h"},"sweat_rate_ml_per_hour":{"description":"The same rate in millilitres per hour. Unit: mL/h.","type":"number","x-unit":"mL/h"},"body_mass_loss_percent":{"description":"(pre − post) / pre × 100; negative when weight was gained. Unit: %.","type":"number","x-unit":"%"},"dehydration_status":{"description":"< 2 % minimal; 2–3 % performance impaired; > 3 % significant (ACSM thresholds).","type":"string"},"fluid_to_replace_ml":{"description":"150 % of the net body-mass deficit, drunk over the hours after exercise (ACSM). Unit: mL.","type":"number","x-unit":"mL"},"recommended_intake_ml_per_hour_next_session":{"description":"Hourly intake that would match the sweat rate in the same conditions (an upper bound: ACSM advises keeping the loss below 2 % of body mass without drinking more than you sweat). Unit: mL/h.","type":"number","x-unit":"mL/h"}}},"formula":"sweat_loss_liters = (pre_exercise_weight_kg − post_exercise_weight_kg) + fluid_intake_ml / 1000 − urine_output_ml / 1000; sweat_rate_l_per_hour = sweat_loss_liters / (duration_minutes / 60); body_mass_loss_percent = (pre − post) / pre × 100; fluid_to_replace_ml = 1.5 × (pre − post) × 1000","method":"Body-mass change is the standard field measure of sweat loss (ACSM 2007); it ignores respiratory water loss and metabolic mass loss, which are small for sessions under about 3 hours. Drinking should not exceed the sweat rate, because over-drinking causes exercise-associated hyponatraemia. Informational, not medical advice.","sources":[{"name":"Sawka MN et al. (2007) American College of Sports Medicine position stand: Exercise and fluid replacement, Med Sci Sports Exerc 39:377-390","url":"https://pubmed.ncbi.nlm.nih.gov/17277604/","type":"peer_reviewed","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":"70 → 69.2 kg, 500 mL drunk, 60 min","inputs":{"pre_exercise_weight_kg":70,"post_exercise_weight_kg":69.2,"fluid_intake_ml":500,"duration_minutes":60},"expected":{"sweat_loss_liters":1.3,"sweat_rate_l_per_hour":1.3,"sweat_rate_ml_per_hour":1300,"body_mass_loss_percent":1.14,"dehydration_status":"Minimal (< 2 % body mass loss)","fluid_to_replace_ml":1200,"recommended_intake_ml_per_hour_next_session":1300},"url":"https://tttkmbb.com/api/v1/calculate/sweat-rate?pre_exercise_weight_kg=70&post_exercise_weight_kg=69.2&fluid_intake_ml=500&duration_minutes=60"},{"name":"62 → 60.5 kg, 750 mL drunk, 100 mL urine, 90 min","inputs":{"pre_exercise_weight_kg":62,"post_exercise_weight_kg":60.5,"fluid_intake_ml":750,"urine_output_ml":100,"duration_minutes":90},"expected":{"sweat_loss_liters":2.15,"sweat_rate_l_per_hour":1.43,"body_mass_loss_percent":2.42,"dehydration_status":"Performance impaired (2–3 % body mass loss)","fluid_to_replace_ml":2250},"url":"https://tttkmbb.com/api/v1/calculate/sweat-rate?pre_exercise_weight_kg=62&post_exercise_weight_kg=60.5&fluid_intake_ml=750&urine_output_ml=100&duration_minutes=90"}],"faq":[{"q":"Why is fluid intake added and urine subtracted?","a":"Weight loss understates sweating when you drank (the drink replaced some sweat) and overstates it when you urinated, so both are corrected to isolate sweat."},{"q":"Should I drink the full sweat rate during exercise?","a":"Not necessarily: ACSM suggests limiting the loss to under 2 % of body mass, which for many people means drinking less than the full sweat rate; drinking more than you sweat is harmful."},{"q":"Why 150 % for recovery?","a":"Urine production continues after exercise, so restoring fluid balance within a few hours needs about 1.5 L for every kilogram lost, ideally with sodium."}],"tags":["sweat rate","fluid loss","hydration","dehydration percent","sweat test","fluid replacement"],"related":[{"calculator_id":"water-intake","reason":"Daily baseline fluid needs outside training."},{"calculator_id":"calories-burned","reason":"Energy cost of the same session."}],"links":{"html":"https://tttkmbb.com/fitness/sweat-rate","markdown":"https://tttkmbb.com/fitness/sweat-rate.md","json":"https://tttkmbb.com/fitness/sweat-rate.json","api":"https://tttkmbb.com/api/v1/calculate/sweat-rate","schema":"https://tttkmbb.com/api/v1/calculators/sweat-rate","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:48:09Z"}