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How to Calculate Your Sweat Rate

Are you drinking enough fluids during exercise? Here is Nutrition Diva's easy way to be sure you're staying hydrated.

By
Monica Reinagel, MS, LD/N, CNS
1-minute read

In order to stay hydrated during hot weather or when exercising, it's important to replace the fluids you're losing via perspiration - which may be more than you realize. Perspiration rates vary greatly from person to person and depending on the conditions. So, one-size-fits-all guidelines may not fit you! Here's an easy method to calculate your personal sweat rate, requiring nothing more than a bathroom scale:

Step #1: Step on the scale before your exercise session.

Step #2: Keep track of how much you drink while exercising.

Step #3: Weigh yourself after exercise and before urinating. (If your clothes are very wet, remove them.) 

Here's how to do the calculations. Half a liter of fluid weighs approximately one pound.  If you weigh exactly the same amount before and after, then your fluid losses were roughly equal to the amount of fluid you took in. Good work! 

If you are one pound lighter, then your sweat losses exceeded your fluid intake by approximately half a liter.  For example, let's say, you weigh 150 pounds before you exercise. You drink a liter of water, which weighs about two pounds . After exercising, you weigh 149 pounds. That suggests that you lost about a liter and a half of sweat, and only replaced a liter. Go have a glass of water!

Note: If you're losing large amounts of fluids through perspiration, you're also losing electrolytes. See this week's podcast for more on what electrolytes do, which foods supply them, and how to ensure you're getting enough. 

About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.