cyclist wiping sweat from his face

Calculate Your Sweat Rate

Here’s the basic formula to determine your sweat rate:

Step 1: Weigh yourself before you ride.

Weigh yourself before you ride. Naked.

For example, let’s say you weigh 155 pounds before you start exercising. (Just like I do, if I’m at my race weight…)

Step 2: Exercise for an hour.

Exercise for an hour in the weather conditions and at the same intensity you expect to face in an upcoming race or long ride.

Step 3: Weigh yourself post-ride.

After your workout, remove your dripping wet shoes, shorts, jersey, etc. Dry yourself off and weigh yourself again. Let’s say you weigh 151 pounds after your workout.

Step 4: Subtract post-ride weight from your pre-ride weight.

To calculate your sweat rate per hour of exercise, subtract your ending exercise weight of 151 pounds from your beginning weight of 155 pounds. The difference of 4 pounds represents your fluid loss during exercise.

Since you should drink 16 ounces of fluid for every pound of fluid you sweat out during exercise, multiply the number of pounds lost by 16. In this example, you should drink 64 ounces of fluid to counteract the symptoms of dehydration and return your body weight to normal.

Step 5: Add in your during-ride fluid intake.

If you drank any fluid during your 60 minutes of exercise, you’ll need to add that number to the total amount of fluid lost during exercise that you calculated in Step 4.

That gives you your final number. The number of ounces of fluid you need to consume per hour of exercise.

There you go. Those five simple steps will tell you how much fluid you need to consume. But remember, you can’t truly reproduce a race in a training ride. And weather conditions are always uncertain.

Once you know your personal sweat rate per hour, you can take fluid breaks so that every 15 minutes you consume 10 to 12 ounces of fluid.

By the end of your 60-minute ride, you won’t be so dehydrated, your performance won’t slow as dramatically, your body temperature won’t be as high, and you won’t have to drink as much fluid the rest of the day.

The Importance of Knowing Your Sweat Rate

It’s a good idea to know a bit about your sweat rate. And you need to test yourself because there are always differences in sweat rates between athletes.

What if you don’t know your sweat rate? Well, let’s ask Chris Leigh, who collapsed just 50 meters from the finish at the 1997 Hawaii Ironman.

He was unaware of just how much he was losing and apparently wasn’t replenishing fast enough.

Your body needs water and electrolytes for proper metabolic function, digestion, and muscle contraction. And to cool yourself down (temperature regulation).

So do the test and the calculation!

Stay hydrated!


This article was originally published on July 30, 2006. It was revised and expanded on April 17, 2018.

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  1. I always sweat more than most people. It’s important to know one’s sweat rate, because not only is hydration needed to optimize performance, but also it’s dangerous to sweat too much.

  2. wait i weigh myself naked?!

  3. @Sara

    Yep. When you weigh yourself, you want to eliminate as many variables as possible.

    This test takes place over a short time period so you don’t have to worry too much, but you definitely don’t want to have clothes on, especially for the post-workout weigh in (when your clothes are soaked in sweat.)

    As such, you wouldn’t want any clothes on for the pre-workout weigh in or you’ll skew the results.

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