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Sweat Rate: from a Weigh-In Test
Your precise personal number: weigh yourself before and after a workout to learn how much to drink per hour.
kg
kg
L
min
How to measure: weigh yourself nude before and right after the session (towel off first) and count what you drank. 1 kg of weight lost β 1 L of fluid. Repeat in different weather β sweat rate depends heavily on temperature.
Why Use This Calculator?
Proper hydration is crucial for athletic performance. Even mild dehydration (2-3% body weight loss) can significantly impair performance, increase heart rate, and reduce cognitive function.
What This Calculator Does
- β’Estimates fluid loss based on your weight, training intensity, temperature, and humidity
- β’Calculates your daily base hydration needs based on lean body mass
- β’Shows how dehydration affects heart rate accuracy (HR drift)
- β’Warns you when fluid loss reaches critical levels
How to Use
- 1.Enter your weight and body fat percentage
- 2.Set the ambient temperature and humidity
- 3.Choose your training intensity zone (Zone 1-5) or use Multi-Zone mode for varied workouts
- 4.Enter the workout duration and any water you plan to drink
- 5.Click Calculate to see your estimated fluid loss and recommendations
Understanding Intensity Zones
Intensity zones are based on heart rate or perceived effort:
- Zone 0 (Rest): Resting state, base metabolism without activity
- Zone 1 (Recovery): Very light effort, easy conversation
- Zone 2 (Endurance): Light effort, can hold conversation
- Zone 3 (Tempo): Moderate effort, conversation difficult
- Zone 4 (Threshold): Hard effort, only short phrases
- Zone 5 (VO2max): Maximum effort, no conversation possible
The Science Behind It
- β’Water loss decreases over time as your body adapts (100% β 90% β 85% β 75% β 65%)
- β’High humidity (>60%) increases fluid loss by 20-30%
- β’Dehydration above 2.5% body weight causes measurable HR drift
- β’Above 8.5% body weight loss, performance drops significantly and data becomes unreliable
