Why should I know my sweat rate?

Knowing your sweat rate helps you create a personalized hydration plan. Dehydration of just 2% body weight impairs endurance performance by 10-20%. By replacing a portion of fluid loss during exercise, you maintain performance and reduce heat illness risk.

How do I measure my sweat rate?

Weigh yourself nude before and after exercise. Track all fluid consumed during exercise. The weight difference plus fluid consumed equals total sweat loss. Divide by exercise duration in hours for your sweat rate. Test in conditions similar to your target event.

How much should I drink during exercise?

Replace 60-80% of sweat losses during exercise. Do not try to replace 100% — it is difficult to absorb that much and risks hyponatremia (low sodium). A general guideline is 400-800 mL/hour, adjusted to your individual sweat rate.

Does sweat rate change?

Yes. Sweat rate increases with temperature, humidity, exercise intensity, and fitness level (fitter people sweat more efficiently). Heat acclimation increases sweat rate by 10-25%. Test in the conditions you will be competing in.

Sweat Rate Calculator

Estimate your hourly sweat loss and personal hydration replacement target from a pre/post exercise weigh-in.

Calculator

How the Calculator Works

Enter your pre-exercise weight, post-exercise weight, fluid consumed during exercise, and exercise duration. The calculator determines your sweat rate, total fluid loss, dehydration percentage, and recommended replacement rate.

Dehydration Thresholds

<1% body weight loss: well hydrated. 1-2%: mild dehydration, early performance decline. 2-4%: moderate dehydration, significant impairment. >4%: severe dehydration, risk of heat illness. Aim to stay under 2% loss during exercise.

Dehydration Effects

Body Weight LossEffect

< 1%No significant effect

1-2%Thirst, reduced endurance

2-3%Impaired thermoregulation, performance drops 10-20%

3-4%Headache, reduced strength

> 4%Heat exhaustion risk, cognitive impairment

Medical Disclaimer

This calculator provides estimates based on weight change. It does not account for respiratory water loss, metabolic water production, or bladder contents. For precise measurement, repeat the test multiple times in similar conditions.

Sweat Rate Calculator

How the Calculator Works

Dehydration Thresholds

Dehydration Effects

Medical Disclaimer

Frequently Asked Questions

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Track Your Sweat Rate Over Time