Sweat Rate Calculator
Your sweat rate is the body mass you lose plus the fluid you drank, divided by the hours you trained. Weigh yourself before and after a timed session, log what you drank, and this calculator returns your sweat loss per hour, the percent of body mass you lost, and exactly how much fluid to replace.
Run the naked weigh-in test below to get your Sweat Rate Plan, then feed the result straight into your sodium plan.
EB says
0.5-2 L/hr
Sweat rate
Log your before-and-after weigh-in, fluid intake, and session length, then hit calculate. Your sweat rate, percent body-mass lost, and drink target appear here.
Gear up
Gear for an accurate sweat test
A sweat test is only as good as your scale and your fluid log. Test any new hydration strategy in training first.
- Digital bathroom scale (0.1 lb resolution)A sweat test is only as accurate as your scale. Pick one that reads to 0.1 lb or 0.05 kg.View on Amazon →
- Reusable insulated water bottlePre-measure your fluid so you know exactly how much you drank during the test.View on Amazon →
- Endurance360 CompleteReplace the sodium you just measured you are losing.Shop Endurance360 →
- High-sodium electrolyte drink mixCarry your replacement fluid as electrolytes, not plain water, once you pass an hour.View on Amazon →
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Replace what you lose
Sodium Calculator
Turn your sweat rate into a per-hour sodium and fluid target with a pre-race loading plan.
Build the bottle
DIY Sports Drink Calculator
Mix the fluid you need to replace with matched carbs and electrolytes.
What is a normal sweat rate?
A typical endurance athlete sweats 0.5 to 2.0 liters per hour. Most runners and cyclists in mild conditions land near 0.8 to 1.4 L/hr, while large athletes working hard in heat can exceed 2.5 to 3.0 L/hr. There is no single normal number; sweat rate rises with body size, intensity, heat, and humidity, which is why you measure your own rather than copy someone else's.
| Conditions | Typical sweat rate | Notes |
|---|---|---|
| Easy effort, cool weather | 0.4 - 0.8 L/hr | Low fluid demand |
| Moderate effort, mild | 0.8 - 1.4 L/hr | Most athletes, most days |
| Hard effort, warm/humid | 1.4 - 2.2 L/hr | Plan deliberate intake |
| Large athlete, hot race | 2.2 - 3.0+ L/hr | Hard to fully replace |
Run the calculator above with your own before-and-after weights to find your exact rate, then aim to keep fluid loss under about 2 percent of body mass.
Sweat rate calculator FAQ
How do I measure my sweat rate?
Weigh yourself nude (or in dry minimal clothing) right before a one-hour run or ride, then towel off and weigh again right after, using the same scale. Track every ounce of fluid you drank during the session. Each kilogram of body-mass lost equals about 1 liter (1,000 mL) of sweat, so add back what you drank to get your true sweat volume. This calculator does that math and converts it to a per-hour rate.
How much fluid should I drink per hour?
Replacing roughly 75% of your measured sweat rate during a session is a practical target: full replacement is hard on the gut and rarely necessary for efforts under a few hours. If you sweat 1,000 mL (about 34 oz) per hour, aim for around 25 oz per hour while moving and top up afterward. This tool calculates that recommended drinking rate from your test result.
Is losing 2% body weight bad?
Up to about 2% body-mass loss is generally tolerated without a clear performance penalty, which is why this calculator treats under 2% as the safe range. At 2% to 3% endurance performance becomes measurably impaired, and beyond 3% the impairment grows and recovery suffers. The goal is not to finish at zero loss but to keep your loss under that 2% line.
Can I drink too much during exercise?
Yes. If you gain weight during a session you drank more than you sweat, which dilutes blood sodium and raises hyponatremia risk, a dangerous condition in long, cool events. This is why the calculator flags weight gain as overdrinking. The fix is to drink to thirst rather than on a fixed schedule, and to make sure your fluids carry sodium once you pass an hour.
Does my sweat rate change with the weather?
A lot. Heat and humidity push sweat rate up sharply, while cool conditions suppress it, so a test done on a cool day can badly understate your losses on a hot race day. Test in conditions close to your goal event, and re-test across seasons. The climate selector here adds context to your result but does not change the measured number.
How accurate is the naked weight method?
It is the most practical field method and is accurate enough to build a hydration plan, but it has limits. Respiratory water loss, any food eaten, and bathroom stops add noise, so weigh under consistent conditions and avoid eating mid-test. For the cleanest number, keep the session around 60 minutes, towel off thoroughly before the after-weigh, and repeat the test a few times to average it.
See also: how to calculate your sweat rate and how much sodium you lose sweating.
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