SportingDrinks

Sweat rate calculator

Weigh yourself before and after a session, note what you drank, and get your sweat rate per hour. Then carry it into the hydration calculator for a plan built on your own numbers.

Your session

Units

Optional. Leave blank if none.

Session length

Your sweat rate

Example: 160 lb before, 158 lb after, 20 fl oz drunk, 90 minutes. Enter your own numbers to replace it.

Sweat rate

1.00 L an hour

999 mL or 33.8 fl oz an hour

Body weight change

−1.3%

That is within 2% of your starting weight, the level ACSM uses as its limit for fluid loss during exercise.[6]

Estimated sodium loss

230 to 1,610 mg an hour

Your sweat rate times the typical sweat sodium range of 230 mg/L to 1,610 mg/L.[1] Only a sweat test narrows this down.

This is how much you lost, not how much to drink. Drink to thirst, and stay under your sweat rate.

Use this in the hydration calculator

How the sweat rate calculator works

Sweat rate is the weight you lost, plus what you drank, minus any urine, divided by the hours you exercised.One kilogram of weight change counts as one liter of sweat.[6] The result is shown in liters and fluid ounces per hour.

The calculator also shows how much of your starting weight you lost. ACSM uses a loss of more than2% as the point where dehydration starts to hurt endurance performance.[6]

Sodium loss is an estimate. Sweat holds about 230 mg/L to 1,610 mg/L of sodium, depending on the person.[1] Your sweat rate times that range gives the low and high figures. Only a sweat sodium test can tell you where you sit.

How to measure your sweat rate

  1. Go to the toilet, then weigh yourself with little or no clothing. Write it down.
  2. Train as normal for at least an hour, in the conditions you want a figure for.
  3. Keep track of everything you drink. Weigh or measure your bottles before and after if you can.
  4. If you pass urine during the session, estimate the amount. Most people can leave this blank.
  5. Towel off well, then weigh yourself again in the same clothing as before.
  6. Enter the numbers above. Repeat in hot and cool weather, because your rate changes with conditions.

Our guide on how to calculate sweat rate covers the method in more detail, including common mistakes. When you have a figure, use it in thehydration calculator.

FAQ

How do I calculate my sweat rate?

Weigh yourself before and after exercise, with as little clothing as possible and after towelling off. Add the fluid you drank and subtract any urine you passed. Divide the result by the session length in hours. The calculator above does this for you, in pounds or kilograms.

What is a normal sweat rate?

Most athletes sweat about 0.5 L/h to 2 L/h, but it depends on body size, pace, heat, humidity and fitness. Two people doing the same session can sweat very different amounts, which is why measuring your own rate is worth it.

Why does 1 kg of weight loss count as 1 liter of sweat?

Sweat is mostly water, and a liter of water weighs about a kilogram. Over a single session, almost all short-term weight loss is fluid, so the change on the scale is a good stand-in for sweat lost. In pounds, the calculator converts to kilograms first.

How much weight loss during exercise is too much?

The American College of Sports Medicine uses a loss of more than 2% of body weight as the point where dehydration starts to hurt endurance performance. Finishing heavier than you started is also a warning sign, because it means you drank more than you sweated.

How do I use my sweat rate?

Press "Use this in the hydration calculator" under your result. The hydration calculator then uses your measured rate instead of an estimate, and shows fluid, sodium and carb targets per hour with matching drinks. Keep drinking to thirst: your sweat rate is a ceiling, not a target.