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How to calculate your sweat rate

Electrolytes are a helpful tool for hikers and trail runners. Electrolytes include sodium, potassium, magnesium, calcium, chloride, phosphate, sulfate, and bicarbonate. Consuming these during exercise that lasts for more than 90 minutes is beneficial, especially as sweat is lost.

Some sports drinks, such as Nuun, or salt tablets have 200-350mg of sodium per serving. Be sure to consume the suggested amount of water with each serving.

1 lb of sweat = 450-700mg of sodium

Often when we think of exercising in heat, we think "DRINK WATER!" Now, you're not completely wrong, but constantly drinking only water can also lead to hyponatremia.

Hyponatremia happens when there's not enough sodium in your bodily fluids. In most cases, this condition occurs in those exercising for 4+ hours, mainly females, with lower body weight, slower running pace, and hot temperatures. To prevent this from happening, you can calculate your sweat rate to hydrate accordingly.

Sweat rate calculation:

pre-weight - post-weight + fluids during activity


Pre-weight: 150 lb

Post-weight: 149 lb

Fluids: 16 oz

Duration: 1 hour

150 - 149 = 1 lb lost (16 oz) + 16 oz fluid consumed = 32 oz (2 lb) sweat loss/hour

The average sweat rate for runners is 23.7-44 oz per hour, according to a two-year study by Dr. Noakes.

Things to note:

Every body is different in how much it sweats. You may sweat more or less than your gal pal you run with.

Clothing color and type of fabric will affect your sweat rate, too. Darker clothing and less-breathable clothing will likely increase your sweat rate, especially in hotter climates.

All data has been sourced from UESCA.


Katharine Moustakes
Hey, friend!

I'm Katharine.

I'm a personal trainer, running coaching, and nutrition coach who's stoked about lifting, the outdoors, summit snacks, and my dog.


I understand that fitness is not your whole life. Fitness is a PART of your life. I approach training in a way that adds value to your life and longevity, so you can enjoy being active whether you're romping around in the mountains, playing with your kids, or signing up for your first 10K race.

I'm here to meet you where you are, so you can train safely and effectively, and gain strength and confidence both in the gym and on the trails.

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