For training
Sweat Rate Calculator
Quick answer
To calculate sweat rate, weigh yourself before and after exercise, add the fluid you drank, subtract any urine, and divide by workout time. The result is your sweat loss in litres per hour. Use it to plan before, during, and after fluids for similar workouts, with heat and sodium-loss cues for long or salty sessions.
Sweat rate
About 51 fl oz/hour. Estimated sweat loss: 1.5 L.
- Before training
- Start with 0.5-0.7 L in the 2-3 hours before similar sessions; finish most of it 30 minutes before start.
- During similar workouts
- Sip about 0.5-1 L/hour, then adjust for thirst, stomach comfort, and heat.
- After training
- Replace roughly 1.9 L over the next few hours, spread steadily and staying at or below about 1 L per hour. Add sodium if the session was long, hot, or salty.
- Sodium loss
- Estimated sodium loss: 600-1050 mg (550 mg/L cue). Food or electrolytes matter more when the session is hot, long, or salty.
- Body-mass loss
- You lost about 1.1% of body weight. Try to stay below 2% on race-day practice sessions.
Private test journal
Learn your sweat-rate range
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- Observed range
- 0-0 L/h
Recent tests
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Why sweat rate matters
Sweat rate is the missing number in most hydration advice. Body weight gives you a daily baseline, but sweat rate tells you how fast you lose fluid during a specific sport, pace, and weather pattern. Measure it on a normal workout first, then repeat in hotter conditions.
How to use the result
For similar sessions, drink enough to keep body-mass loss below about 2%, while avoiding the urge to force down more than your stomach can handle. After the session, replace about 125–150% of the remaining fluid loss over the next few hours, with sodium when the session was long, hot, or salty.
Heat and sodium cues
Heat and salty sweat do not turn the calculator into a prescription, but they make the plan more realistic for athletes. Use the sodium estimate as a practical cue for food or electrolytes during longer, hotter sessions, and avoid using sodium drinks to justify forced over-drinking.
Frequently asked
What is a normal sweat rate?
Many athletes fall around 0.5–1.5 L per hour, but the real range is wide. Heat, humidity, intensity, clothing, body size, and acclimation can move your number a lot, which is why measuring beats guessing.
How do I calculate sweat rate?
Weigh yourself before and after exercise, add the fluid you drank, subtract any urine, then divide by workout hours. One kilogram of body-weight loss is treated as about one litre of fluid.
Should I replace 100% of sweat during exercise?
Usually no. Trying to match every drop can upset your stomach and raises over-drinking risk. A better target is to limit body-mass loss to under about 2% and replace the rest after training.
How do heat and salty sweat change the plan?
Hot sessions and salty sweat raise the usefulness of sodium and make pacing more important. Use the heat and sweat-saltiness controls as a planning cue, then adjust for thirst, stomach comfort, and medical guidance.
Sources
- 1.American College of Sports Medicine, Exercise and Fluid Replacement — Athletes should start exercise euhydrated, limit body-mass losses during training, and replace fluid and sodium after heavy sweat losses.
- 2.Sawka et al., ACSM Position Stand — Sweat rate varies widely by athlete, heat, intensity, clothing, and acclimation, so pre/post body-weight checks are the practical way to individualise fluid plans.
- 3.Mayo Clinic — General guidance of roughly 2.7–3.7 L of total fluids a day, with thirst and pale-yellow urine as everyday checks.