In 30 seconds
- Your sweat rate is the weight you lose while training, plus what you drink, minus what you pass as urine, divided by the hours. One kilo equals one litre.
- Athletes usually sweat between 0.5 and 2.0 litres an hour. More than 3 litres is rare: it happens to about 2%.
- Weigh yourself in very little clothing: soaked clothing hid 8-10% of sweat in a study with female runners.
- With your figure, plan ahead: during, drink to thirst without exceeding 80% of what you sweat; afterwards, 1.25-1.5 litres per kilo lost.
Your sweat rate is how much fluid you lose per hour of training. You calculate it with a set of scales: weight before − weight after + what you drank, divided by the hours of training. It is the simplest method there is and the most accurate 1.
How much athletes sweat
Litres of sweat per hour: the usual range
Why it is worth knowing
Because everyone sweats very differently. The range goes from 0.3 to 2.5 litres per hour depending on the person, the intensity and the weather 3. In athletes, the usual figure is between 0.5 and 2.0 litres per hour, and only around 2% exceed 3 litres 1.
In a study with more than 1,300 athletes, the average by sport was as follows 2:
| Sport | Sweat per hour | Sodium per hour |
|---|---|---|
| American football | 1.51 L | 1,286 mg |
| Endurance sports | 1.28 L | 1,189 mg |
| Basketball | 0.95 L | 794 mg |
| Football | 0.94 L | 796 mg |
| Baseball | 0.83 L | 626 mg |
Source: Barnes et al., 2019. 1,303 athletes. Sodium converted from mmol to mg (1 mmol = 23 mg).
With your own figure you stop guessing: you know how much to carry in your bottle, how much sodium you need and how much to drink when you finish. If you play padel or football, we apply it to the match in isotonic drink for padel and football.
What you need
- A set of bathroom scales, always the same one.
- A towel to dry yourself before weighing.
- Your bottle, so you know how much you drink. The easiest way is to fill it with a known amount and measure what is left.
- A normal training session of at least an hour.
The method
Your sweat rate in 3 steps
Step 1: weigh yourself before
Go to the toilet before weighing yourself and step on the scales naked or in very little clothing 1. Ideally, weigh yourself twice and take the average 1. Write the figure down.
Step 2: train and note down what you drink
Train as usual and note down exactly how much you drink. If you eat something, note that down too: it counts just like what you drink.
If you go to the toilet during the session, note roughly how much urine you passed. Urine is not sweat, so it has to be subtracted 1.
Step 3: weigh yourself after and calculate
Dry yourself well, take off your wet clothes and weigh yourself again on the same scales, naked or in very little clothing, just like before 1. Then apply the formula:
(weight before − weight after + litres drunk − urine) ÷ hours of training = litres per hour
Each kilo of weight lost counts as one litre of sweat.
A worked example
Where the cyclist's 1.85 litres of sweat come from
A worked example
| Step | Data | Result |
|---|---|---|
| Weight before | 78.0 kg | — |
| Weight after | 76.9 kg | You have lost 1.1 kg |
| What you drank | A bottle and a half: 0.75 L | Add it: 1.1 + 0.75 = 1.85 L |
| Urine during the ride | None | Nothing to subtract |
| Duration | 1.5 hours | 1.85 ÷ 1.5 = 1.23 L per hour |
| Weight lost as a share of the total | 1.1 ÷ 78 | 1.4% of your weight |
Formula: (weight before − weight after + fluid drunk − urine) ÷ hours. Baker, 2017.
This cyclist sweats 1.23 litres per hour and has finished 1.4% lighter. That is below 2%, the limit it is recommended not to exceed during exercise 4.
The mistakes that skew the result
- Weighing yourself in wet clothes. The sweat left in your clothes does not count as lost. In a study with female runners, racing kit hid 8-10% of their sweat 1.
- Not subtracting urine. If you pass urine and do not note it down, you overestimate your sweat. In one study, not subtracting it inflated the result by 16% in the heat and by 37% in the cold 1.
- Forgetting what you drink or eat. Everything that goes in adds up.
- Measuring only once. Your sweat rate varies by 5-7% from one day to the next even if you repeat the same session 1.
In sessions of more than 2-3 hours, very intense ones or in dry air, you also lose weight through breathing and through the fuel you use: between 5% and 15% of the weight lost 1. For normal sessions, there is no need to correct for it.
Repeat it in different conditions
Your figure changes with intensity, heat, humidity, sun, wind, your body size and heat acclimatisation 1. Measure it in two or three different sessions, one in the heat and one in cooler weather, and settle on a range.
A change of more than 5% in your sweat rate may already justify adjusting what you drink 1.
What to do with your figure
| When | Recommendation | In the example |
|---|---|---|
| During | Drink to thirst, without replacing more than 80% of sweat | Up to about 0.98 L per hour |
| Sodium | 400-1,100 mg per litre from one hour onwards | Important: sweats more than 1.2 L per hour |
| After | 1.25-1.5 L for every kilo lost | 1.4-1.65 L over the following hours |
Sources: Mosler et al., 2020; Thomas et al., 2016.
- During: drink to thirst and do not replace more than 80% of what you sweat 3. As a guide, 0.4-0.8 litres per hour is usually tolerated during intense efforts 4.
- Sodium: it is recommended when you sweat more than 1.2 litres per hour, your sweat is salty or exercise lasts more than 2 hours 4. We explain it in how much salt you lose when you sweat.
- After: replace between 1.25 and 1.5 litres for every kilo lost 4. You will find it in detail in how to rehydrate after training.
And one simple check: if you weigh more at the end than at the start, you have drunk too much. It is the main cause of exercise-associated hyponatraemia 5.
If you would rather not do the maths, the hydration calculator applies the formula for you and gives you your plan for before, during and after. For race day, use the race hydration planner.
Your figure and Nitrus
With your sweat rate you know how many bottles you need. Each serving of Nitrus Isotonic is 25 g in 400-500 ml of water. It contains about 195 mg of sodium and 15 g of carbohydrate, plus five electrolytes and all 13 vitamins. Here is how it works out depending on the dilution:
| Preparation | Sodium per serving | Sodium per litre | Carbohydrates per serving | Carbohydrates per litre |
|---|---|---|---|---|
| 25 g in 400 ml | 195 mg | 488 mg | 15.1 g | 37.8 g |
| 25 g in 500 ml | 195 mg | 390 mg | 15.1 g | 30.3 g |
Each 25 g serving contains 0.488 g of salt (about 195 mg of sodium), 148 mg of potassium and 15.13 g of carbohydrates.
If you sweat a lot or it is hot, make it up with 400 ml: that is the dilution with the most sodium per litre.
Frequently asked questions
How do you calculate sweat rate?
Weigh yourself before and after training in very little clothing. Add what you drank to the weight lost, subtract any urine you passed and divide by the hours of training. One kilo equals one litre of sweat.
How much does a person sweat per hour during exercise?
Between 0.3 and 2.5 litres per hour depending on the person, the intensity and the weather. In a study with more than 1,300 athletes, endurance athletes sweated an average of 1.28 litres per hour.
How often should I measure my sweat rate?
Measure it in two or three different sessions, in hot and cool weather, and repeat it when the season or your fitness changes. A change of more than 5% may already justify adjusting what you drink.
Do you need to replace everything you sweat during training?
No. The recommendations advise drinking to thirst and not replacing more than 80% of what you sweat while you train. The rest is replaced afterwards, with 1.25-1.5 litres per kilo lost.
Sources
- Baker LB. Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Med. 2017;47(Suppl 1):111-128. View publication
- Barnes KA, Anderson ML, Stofan JR, et al. Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: an update and analysis by sport. J Sports Sci. 2019;37(20):2356-2366. View publication
- Mosler S, Braun H, Carlsohn A, et al. Position of the working group sports nutrition of the German Nutrition Society (DGE): fluid replacement in sports. Dtsch Z Sportmed. 2020;71(7-9):178-184. View publication
- Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. J Acad Nutr Diet. 2016;116(3):501-528. View publication
- Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Br J Sports Med. 2015;49(22):1432-1446. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product. A varied and balanced diet and a healthy lifestyle are important.
