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Sports

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Sports

Sweat Rate Calculator.

Estimates your sweat rate in liters per hour based on pre- and post-exercise body weight, fluid intake, and exercise duration.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Weigh yourself immediately before exercise, wearing minimal clothing.

  2. 2

    Record your weight after exercise, towel-dried, with the same clothing.

  3. 3

    Note the total fluid you consumed during the session in liters.

  4. 4

    Subtract post-weight from pre-weight, add fluid intake, then divide by hours exercised.

((pre_weight - post_weight) + fluid_intake) / (duration / 60)

Frequently asked questions

Why do I need to account for fluid intake?

Because you lose water through sweat, but drinking replaces some of it. Adding intake gives the true total sweat loss.

What if I used the bathroom during exercise?

For accuracy, avoid bathroom breaks or adjust for urine loss. Otherwise, the estimate may be slightly off.

How can I use my sweat rate?

Use it to plan hydration: drink roughly the same amount per hour during similar workouts to maintain fluid balance.

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Results

Formula checked

Sweat Rate

1,3L/hour

Total Sweat Loss1,30L
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Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Estimates your sweat rate in liters per hour based on pre- and post-exercise body weight, fluid intake, and exercise duration.

  1. Weigh yourself immediately before exercise, wearing minimal clothing.
  2. Record your weight after exercise, towel-dried, with the same clothing.
  3. Note the total fluid you consumed during the session in liters.
  4. Subtract post-weight from pre-weight, add fluid intake, then divide by hours exercised.

Formulas

The math behind this calculator, written out so you can verify the result.

Sweat Rate

Sweat Rate (L/h) = (Pre-weight - Post-weight + Fluid Intake) / Duration (h)

This formula estimates how much fluid you lose per hour through sweating, combining weight change and fluid consumed.

Example:

Input: Pre=70kg, Post=69.2kg, Intake=0.5L, Duration=1h

Calculation: (70 - 69.2 + 0.5) / 1 = 1.3

Result: 1.30 L/h

Real-world use cases

Where this calculation shows up in everyday life.

Hydration planning

Know your sweat rate to determine how much to drink during training or races.

Example: If you sweat 1.2 L/h, aim to drink about 1.2 L per hour.

Monitoring dehydration risk

Track changes in sweat rate over time to spot overhydration or dehydration patterns.

Example: A sudden drop may indicate heat acclimatization or illness.

Customizing nutrition strategy

Combine sweat rate with electrolyte needs to tailor sports drinks.

Example: High sweat rates may require extra sodium.

Tips and common mistakes

Tips

  • Weigh yourself on the same scale for consistency.
  • Use the same clothing or subtract its weight for accuracy.
  • Record fluid intake in liters, not cups, for precise math.
  • Perform the test under similar conditions (temperature, intensity) for reliable data.

Common Mistakes to Avoid

  • Forgetting to include fluid intake, which underestimates sweat loss.
  • Using duration in minutes without converting to hours.
  • Weighing at different times of day or with different clothing.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.