Ever wonder how much you sweat during a workout? Knowing your sweat rate can be a valuable tool to help keep you hydrated and performing at your best. Whether you are starting a couch to 5k program or eyeballing your next triathlon.
We are here to help you figure out your sweat rate and map out your hydration plan to unlock your best results!
Sweat Rate is a calculation that is used to determine the number of fluids that someone loses during exercise. This number is regularly measured by athletes, coaches, and sports scientists to develop effective hydration strategies pre, during, and post-exercise. Modest levels of dehydration (around 2% of one’s body mass) can impair performance during long-duration exercise in the heat and some evidence shows it can even negatively impact short-duration interval-style training performance as well. As a result, anyone interested in performing at the best make it a priority to be hydrated.
Research on the sweat rates of athletes in hot environments has shown their sweat rates to range from 16.9-59.1 oz/hr. (in other words, anywhere from about 2 to 7 cups of water). With larger athletes like football players showing sweat rates that average as high as 71.0 oz/hr. (over half a gallon!). 
The major electrolytes in our body are bicarbonate, calcium, chloride, magnesium, phosphate, potassium, and sodium. Electrolytes play crucial roles in the normal functioning of the body including fluid regulation, muscle contraction, and regulating pH levels. When we sweat, in addition to losing fluid we also lose electrolytes, with sodium being the one that is most excreted. Sweat sodium concentrations will vary among people, however as exercise intensity increases the percentage of our sweat sodium losses tends to increase as well. [3,4] In one study sodium and chloride losses increased by 150% when exercise intensity increased from 45 to 65% VO2max. 
Your sweat rate can be calculated with a simple formula that requires you to measure your body weight, fluid consumption, and the amount of time you exercised. When you are calculating your workout, you should stick to workouts lasting 45 minutes to 2 hours, with 1-hour workouts being the most ideal. Workouts that are shorter or longer than this time range may be prone to more errors from confounding variables like glycogen loss.
Because our sweat rates can vary depending on numerous factors like the type and intensity of exercise, the environmental conditions, and the type of clothes we’re wearing it is important to test your sweat rate in conditions that are most like the environment that you train or compete. 
- A - Body weight pre-exercise (using minimal clothing):
- B - Body weight post exercise (using minimal clothing):
- C - Change in body weight (A – B) x 16 ounces:
- D - Amount of fluid consumed during exercise:
- E - Total fluids used during exercise (C+ D):
- F -Duration of exercise:
- G - Sweat Rate:
Example 1: Long Duration Cycling Workout
- Bodyweight pre-exercise: 165 pounds
- Bodyweight post-exercise: 162 pounds
- Change in bodyweight x 16 ounces: 3 x 16 = 48 ounces
- Amount of fluid consumed during exercise: 19 ounces
- Total fluids used during exercise: 67 ounces
- Duration of exercise: 1 hour 30 minutes
- Sweat Rate = 67/1.5 = 44.6 ounces per hour
Example 2: Moderate Intensity Running Workout
- Bodyweight pre-exercise: 165 pounds
- Bodyweight post-exercise: 163 pounds
- Change in bodyweight x 16 ounces: 2 x 16 = 32 ounces
- Amount of fluid consumed during exercise: 15 ounces
- Total fluids used during exercise: 47 ounces
- Duration of exercise: 1 hour
- Sweat Rate = 47/1 = 47 ounces per hour
Determining Sweat Rates For Your Activities
For increased accuracy, it is best to calculate your sweat rate over several workouts, especially if the environment, intensity, and types of your workouts vary. Our day-to-day whole-body sweat rates can vary by 5-7%.
If you exercise indoors and outdoors, knowing your sweat rate for both environments can be advantageous especially if you live in an area with higher climates. Heat acclimatization training (the exposure to heat during training) can significantly increase one’s sweat rate. Knowing your sweat rates depending on the intensity of your workouts can also help you stay appropriately hydrated even for your toughest workouts.
And finally, if you do many distinct types of exercise like a triathlete as an example, knowing your individual sweat rates for running, cycling, and biking can help you better prepare your hydration strategies for training and race day.
Plan Your Pre, During, & Post Workout Hydration
Map out your hydration plan around your workout so that you can perform at your best. A good guide to follow [9,10,11]:
1) Drink 13 – 20 oz of fluids before your workout.
2) Drink 16 – 67 oz of fluids during your workout. Now that you know your average sweat rate, you will have a better idea of if you should be consuming towards the low or high end of that range. Generally, athletes do not tolerate fluid volumes greater than 20-27 oz. So it is best to divide your fluid intake during your workout rather than trying to chug it all at once.
3) Drink enough fluid after your workout to make up for 150% of weight loss. As an example, if you lost 32 oz of fluid during a workout, you would aim to drink 48 oz of fluid to make up for it. Given that our stomach can only absorb a certain amount of fluid at a time, you will also want to space this fluid out rather than chugging it at once.
Choose Drinks That Taste Good
Let’s face it, one of the challenges of properly hydrating is that many people do not drink enough water because they get bored of the taste. Choosing beverages that you enjoy the taste of and have a rich blend of electrolytes, with an emphasis on sodium can help motivate you to drink more. If your workouts are shorter than 90 minutes (about 1 and a half hours), you may also want to opt for a drink that is zero sugar.
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