Sweat Rate Calculator
Find how much fluid you lose per hour of exercise.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Knowing your sweat rate helps you hydrate properly during exercise, and this calculator finds it from a simple weigh-in. You enter your body weight before and after exercise, any fluid you drank during the session, and the duration, and it returns your total fluid lost and your sweat rate per hour in liters and milliliters. The method works because the weight you lose during exercise is almost entirely water lost as sweat, and one liter of sweat weighs about one kilogram. Adding back the fluid you drank gives your true total loss, and dividing by the hours gives the rate. Sweat rates vary widely, from under half a liter to more than two liters per hour, depending on the individual, exercise intensity, temperature, humidity, and clothing. Knowing your rate lets you plan how much to drink to avoid both dehydration, which impairs performance and can be dangerous, and overdrinking, which is rarely necessary. For accurate results, weigh yourself with minimal clothing, empty your bladder first, and towel off sweat before the post-weigh. Because conditions change your sweat rate, test it in the environment you train or compete in. Use the rate as a target for fluid intake, drinking at regular intervals rather than all at once. Enter your weights, fluid, and duration to find your sweat rate.
Sweat rate = (pre-weight − post-weight + fluid consumed) / hours
Your fluid loss equals the weight you lost during exercise plus any fluid you drank, since one liter of sweat weighs about one kilogram. Dividing that loss by the exercise duration in hours gives your sweat rate, the amount of fluid you should aim to replace for each hour of similar activity.
Source:American College of Sports Medicine hydration guidance
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter body weight before exercise, body weight after exercise and exercise duration.
- 2
Adjust the options
Adjust fluid consumed during if they apply — sensible defaults are already set.
- 3
Read your result
Sweat rate updates instantly as you type — no button to press.
Frequently asked questions
How do I calculate my sweat rate?
Weigh yourself before and after exercise, note any fluid you drank, and record the duration. Your fluid loss is the weight lost plus the fluid consumed, since a liter of sweat weighs about a kilogram. Dividing that loss by the hours gives your sweat rate. The calculator handles the arithmetic once you enter these values.
What is a normal sweat rate?
Sweat rates vary widely, typically from about 0.5 to 2 liters per hour, with some athletes exceeding that in hot conditions. Factors include body size, fitness, exercise intensity, temperature, humidity, and clothing. There is no single normal value; what matters is knowing your own rate so you can plan fluid intake for your conditions.
How should I use my sweat rate?
Use it as a target for how much fluid to replace per hour of similar exercise. Aim to drink enough to limit weight loss during activity to a small percentage of body weight, sipping at regular intervals rather than all at once. Replacing close to your sweat rate helps maintain performance and prevents dehydration during long or intense sessions.
How can I weigh myself accurately for this?
Weigh yourself just before and just after exercise using the same scale, wearing minimal or no clothing, and empty your bladder before both readings. Towel off sweat before the post-exercise weigh-in so you measure water lost, not water sitting on your skin. Accurate weights make the calculated sweat rate reliable.
Does sweat rate change with conditions?
Yes. You sweat more in hot, humid weather and during harder efforts, and less in cool conditions or at lower intensity. Fitness and heat acclimatization also affect it. Because of this variability, measure your sweat rate in the environment where you train or compete, and re-test when conditions change significantly to keep your hydration plan accurate.