How To Calculate Your Sweat Rate At Home

With the dog days of summer lingering on, making sure that you are properly hydrating (and rehydrating) is just as important as ever. If you live in the South, you may be in the stage of the year when the temps cool off for just a moment, giving your mind and body a reprieve, and a false notion that maybe, just maybe, fall is almost here. Let me be your reminder that summer temps are not gone.

I wanted to take some time to actually explain how you can calculate your sweat rate at home, and get a fairly accurate account of the fluids you are losing during a training session, and what you need to rehydrate properly. Knowing this information is useful for a number of reasons, the biggest being it can help you start to dial in your race day nutrition and hydration intake.

Sweat Rate Disclaimers

Before we get into the meat of the calculations I wanted to make sure I am clear that this is just a guideline. There will always be personal factors that will change what each individual might need (how much salt you lose for one). In addition to those factors, there are also environmental factors that may include:

• The type of activity you are doing

• The intensity level of the activity

• The climate conditions during the activity

If you want to dial in your sweat rate further, you can perform multiple tests (in different climate/weather conditions & over various types of training sessions) to get a sweat rate range.

Recording Your Data

Okay, let’s go ahead and get to it. Here are a list of items you need in order to perform this at home:

• A scale

• Access to the current weather

• A towel

If you have these items then you are good to go. Here’s what you need to record your sweat rate:

• Record your weight Before your training session. Note: This is done with No Clothes!

• Record your weight After your training session. Note: Towel dry first, and then take off your clothes before weighing in.

• Record the duration of the training session.

• Record the temperature during the training session.

• Record the type of the training session (bike or run).

• Record the intensity of the training session (aerobic, tempo, threshold, etc.).

• Record the total fluid consumed during the training session.

• Record if you urinated during the training session (and how many times if multiple).***

Calculating Your Sweat Rate

Now that the data is recorded, let’s get to the calculations.

1. Subtract your end weight from your starting weight.

2. Add in the fluids consumed during your training session.

3. Divide by 60 to get the fluid rate loss per hour. This is your sweat rate.

4. ***If you urinated during the training session this needs to be factored in. Assume 200-300 ml and add this to the ending body weight in Step 1.

5. Record average and peak sweat rates from all training sessions you do this for.

Note: Each pound of body weight lost is equivalent to 16 ounces of sweat loss OR each kilogram of body weight lost is equivalent to 1000 ml of sweat loss.

Now What?

Now that you have this information, what do you do with it?

During: The general consensus is to aim to replace about 70% of sweat losses during training sessions. For training and racing, you can multiply your average hourly sweat loss by 0.7 and work toward trying to intake enough fluids during your sessions.

After: To fully recover the general rule is to replace about 150-200% of the body weight lost in the next 12 hours to fully recover. Have another session planned for the day? That recovery time becomes shorter.

Still unclear of how to put this into motion? Consulting a sports nutritionist is always a high recommendation. They can dial in your hydration plan more effectively to make sure you are consuming the best balance of water, electrolytes, calories, etc. for your needs.

If you have more questions, please send me a message by contacting me here.

- Happy Training, and Stay Hydrated!