Free field tool
Find your sweat-rate starting point.
Use representative training runs to estimate fluid loss per hour. Save private field tests and compare conditions over time; none of the results prescribe how much to drink in every race.
Training-session sweat-rate calculator
Weigh before and after a steady, representative run in similar clothing. Record what you drank; include urine only if you measured it.
For a useful field test
Use a run long enough to create a measurable change, weigh with the same dry or minimal clothing before and after, and note conditions. Repeat on more than one day before changing a race strategy.
Measurement units
kg
kg
hours
min
mL
mL
°C
Your session estimate
Enter positive pre-run mass, post-run mass, and duration. If the result is not positive, review your measurements before using it.