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Stay Hydrated: How to Calculate Your Sweat Rate


Maintaining your water level is imperative whenever you’re exercising. As the colorful ads for drinks like Gatorade effectively demonstrate, your body truly pumps into high gear during prolonged exertion, coating you in sweat to maintain an appropriate internal body temperature.

In summer your sweat is extremely visible, and deciding how much water to drink usually doesn’t pose too much of a challenge. However, in winter the sweat will rapidly evaporate if you exercise outside. Those cold temperatures could make it seem like you’re less hydrated than you appear.

Don’t fall victim to this natural trick of winter – if you don’t stay hydrated you could become light-headed, dizzy, or even pass out. If you plan to exercise outside use our handy guide below to calculate your sweat rate and the amount of filtered water you should drink to replace it during a workout:

woman drinking water

In order to calculate your sweat rate you should plan to exercise for one hour at the standard rate that you typically exercise. Do whatever exercises you normally do – if you’re training for a marathon, run for one hour.

Have a scale handy, as you will be weighing yourself before and after your hour of exercise. If you normally drink water during your workout, measure out a pre-determined amount (for example, 20 ounces of water) and drink all of it before the end of your workout.

If you need to urinate do so before exercising. Once you have used the restroom warm-up until you first begin to sweat. Weigh yourself while wearing as little clothing as you can.

Once you have weighed yourself record the weight and then simply work out for one hour. Drink your water at normal intervals, and do not drink any more water than you have allotted to guarantee an accurate measurement.

Once you have completed your workout cool down, dry off with a towel, and then weigh yourself again wearing what you did when you initially measured your weight. Only after weighing yourself and recording the result can you use the restroom.

Now that you’ve finished your trial, here’s how to calculate your sweat rate:

  • Subtract your body weight post-workout from your initial weigh-in
  • Convert this change in body weight to ounces
  • Add the amount of water you consumed during the workout to your change in body weight to calculate your sweat loss
  • This is the amount of water you lose per hour. You can divide this amount by 60 to learn your sweat rate per minute.

For example, let’s say a Pelican Water customer weighed in at 140 pounds before their workout and 138.5 pounds after their workout. 140 – 138.5 = 1.5 pounds, or 16 ounces. Let’s also say this person drank 20 ounces of water during their workout. 20 + 16 = 36 ounces of sweat lost in one hour. So, knowing this, this person would probably drink at least 32 ounces of water after their workout to stay hydrated.

Armed with your typical sweat rate you can estimate about how much water to drink for various exercises, using it as a baseline. Always replace fluids lost with filtered water or specialized sports drinks after a workout to avoid the potential of fainting or experiencing other symptoms of dehydration this winter.

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