Sweat Rate
Weight lost during exercise is almost entirely water. Add what you drank to the weight lost (1 kg = 1,000 mL) for the fluid that actually left, then divide by the hours for an hourly rate.
Your numbers
Sweat rate an hour
1,133mL/h
Water
1,700mL
Percentage
1.71%
What it means
1133 mL an hour — aim to drink close to this rate while training.
Formula
Sweat rate an hour = (Weight lost (kg) × 1000 + Fluid drunk (mL)) ÷ Hours
Losing more than 2% of body weight degrades performance. For a 70 kg athlete that line sits at 1.4 kg.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Weight lost (kg) (kg)Weight lost across the session — almost entirely water. | 1.2 | 0 ~ 5 |
| Fluid drunk (mL) (mL)Fluid you drank during the session. | 500 | 0 and up |
| Hours (h)A duration counted in hours. | 1.5 | 0.25 ~ 12 |
Step by step
Quick reference table
Results when only Weight lost (kg) (kg) changes and everything else stays put.
| Weight lost (kg) (kg) | Sweat rate an hour (mL/h) | Water (mL) | Percentage (%) |
|---|---|---|---|
| 0.6 | 733 | 1,100 | 0.86 |
| 0.9 | 933 | 1,400 | 1.29 |
| 1.2 | 1,133 | 1,700 | 1.71 |
| 1.8 | 1,533 | 2,300 | 2.57 |
| 2.4 | 1,933 | 2,900 | 3.43 |
What each result means
| Result | At default values |
|---|---|
| Sweat rate an hour (mL/h)Fluid lost per hour; drink to match this rate. | 1,133 |
| Water (mL)Water to drink in a day; water inside food is not counted. | 1,700 |
| Percentage (%)A share expressed out of 100. | 1.71 |
Common mistakes
Losing more than 2% of body weight degrades performance. For a 70 kg athlete that line sits at 1.4 kg.
Glossary
- Weight lost (kg)
- Weight lost across the session — almost entirely water.
- Fluid drunk (mL)
- Fluid you drank during the session.
- Hours
- A duration counted in hours.
- Sweat rate an hour
- Fluid lost per hour; drink to match this rate.
- Water
- Water to drink in a day; water inside food is not counted.
- Percentage
- A share expressed out of 100.
Frequently asked questions
Q. How is Sweat Rate calculated?
Sweat rate an hour = (Weight lost (kg) × 1000 + Fluid drunk (mL)) ÷ Hours — Weight lost during exercise is almost entirely water. Add what you drank to the weight lost (1 kg = 1,000 mL) for the fluid that actually left, then divide by the hours for an hourly rate.
Q. Can you walk through an example?
With Weight lost (kg) 1.2kg, Fluid drunk (mL) 500mL, Hours 1.5h, the answer is Sweat rate an hour 1,133mL/h.
Q. What do I need to enter?
Enter Weight lost (kg), Fluid drunk (mL), Hours. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Weight lost (kg) (kg) moves the answer to Weight lost (kg) (kg) 0.6 → Sweat rate an hour (mL/h) 733 and Weight lost (kg) (kg) 2.4 → Sweat rate an hour (mL/h) 1,933. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Losing more than 2% of body weight degrades performance. For a 70 kg athlete that line sits at 1.4 kg.
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