Understanding Your
Sweat Rate🧪

Estimating your sweat rate helps you personalize your hydration strategy and improve your performance in training and competition.

💧 What affects sweat rate?

Your sweat rate is influenced by your size, fitness level, how hard you're working, the weather, clothing, and more. It also varies between activities and from day to day.

🧮 How to calculate your sweat rate

Equipment needed:

  • Accurate body scale
  • Food scale (to measure fluids/fuel)
  • Dry towel

Steps: The goal here is to accurately account for fluid weight loss during exercise. In the most simple terms, what do you weigh before exercise vs after, the difference is the number we are after. Try to measure sessions that are at least 60 minutes long. Shorter workouts can distort your results.

    Note: Sweat losses are best calculated in KGs and Liters.
  1. A = Your weight pre-exercise, ideally nude (in kgs)
  2. B = Your weight post-exercise, dry off with a towel and under same conditions
  3. C = A - B, this is your net sweat weight loss post-exercise
  4. P = You can track this creatively🪣, or subtract 0.3L for each unrination during exercise
  5. T = Exercise duration in hours
  6. X = Weight of food and water you bring to exercise (KGs)
  7. Y = Weight of your remaining food and water post-exercise
  8. Z = X - Y is your net fluid and food intake
  9. Estimate your sweat rate: (C + Z - P) ÷ T
Use the Calculator

Example Sweat Rate Calculation

    C = .9 kgs
    Z = 0.5 kgs
    P = 1 x 0.3L
    T = 1.15 hours

    ( C  +   Z   -  P ) ÷   T   = Sweat Rate
    (0.9 + 0.5 - 0.3) ÷ 1.15 = .73L/h

Note: 1 kg of body weight loss is approximately equal to 1 liter of sweat.

📊 What does your number mean?

  • < 0.5 L/hr = Low
  • 0.5–1.5 L/hr = Moderate
  • > 1.5 L/hr = High
  • > 2.5–3 L/hr = Very High (difficult to replace during long sessions)

These values must be interpreted relative to your body size and sport. For a small athlete, 1.5 L/hr may be very high; for a large football player, it's moderate.

🧠 What to do with this info

Your sweat rate is a guide — not a rigid prescription. Don't aim to replace 100% of losses during activity. Instead, use it to:

  • Get in the ballpark for how much to drink per hour
  • Build a starting point for testing hydration in training
  • Pair with sweat sodium data for complete electrolyte needs

⚠️ Important

Trying to drink 100% of what you lose is often unnecessary — and risky (hyponatremia). Start hydrated, drink to thirst, and adjust with your sweat test insights.

📈 Still curious?

For detailed insights, read the full blog post and explore the original research: Jay et al., 2024 - Journal of Applied Physiology.

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