Free Sweat Rate & Sodium Loss Calculator
Calculate your personal sweat rate, sodium loss and in-session hydration targets from pre/post-workout weight. Built for endurance athletes and sports dietitians.
Weigh yourself nude or in dry kit right before starting
Towel off and weigh again in the same state
Total water, sports drink or gels taken during the session
How salty is your sweat?
References & sources
- [1]Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390.
- [2]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.
- [3]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.
- [4]Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568.
- [5]Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol. 2014;4(1):257-285.
Medical disclaimer
This calculator is for educational and informational purposes only. It is not a substitute for individualised medical, nutritional, or clinical advice from a qualified healthcare professional. Results are estimates based on published guidelines and may not reflect your specific circumstances. Always consult a registered dietitian, physician, or relevant specialist before making significant changes to your diet, medications, or clinical care.
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Perguntas Frequentes
How do I measure my sweat rate accurately?
Weigh yourself nude (or in dry clothing of known weight) immediately before a training session. Train at your typical intensity for a measured duration. Towel off and reweigh in the same state, tracking any fluid you drank during the session. Sweat loss (kg) = pre-weight − post-weight + fluid consumed (where 1 ml ≈ 1 g). Divide by hours to get sweat rate in L/hr.
What is a normal sweat rate?
Most athletes sweat between 0.5 and 2.0 L/hr. Endurance athletes in hot conditions can exceed 3 L/hr. Rates vary with body size, fitness, heat acclimation, intensity, humidity, and clothing. Your baseline matters more than any "average" — track trends over multiple sessions.
How much sodium do I lose in sweat?
Sweat sodium concentration ranges from about 200 to 2,300 mg per litre, with an average near 950 mg/L. Genetics drive most of the variation; training and heat acclimation shift it only slightly. A "salty sweater" can lose 1,500 mg of sodium per litre or more — significant over long sessions.
Should I drink to thirst or follow a plan?
For sessions under 60 minutes in moderate conditions, drinking to thirst is generally sufficient. For sessions over 90 minutes, in hot or humid conditions, or when sweat rate exceeds 1 L/hr, planned fluid and sodium intake outperforms thirst cues. Aim to keep body mass loss under 2%.
When does dehydration affect performance?
Body mass loss of 2% or more consistently impairs endurance performance, thermoregulation, and cognitive function. Losses above 4% raise the risk of heat illness. If your calculation shows >2%, you need more in-session fluid; if <1%, your current intake is on track.