Recovery
As of 2026-04-24
How Sweat Rate Calculator works
Methodology for the Sweat Rate Calculator: formulas, coefficients, data sources, assumptions, and known limitations.
Scope
Measures personal sweat rate from pre/post-exercise weigh-ins and estimates fluid and sodium losses.
Formula
sweat_rate_l_per_h = (pre_kg - post_kg + fluid_l - urine_l) / hours. sodium_loss_mg = sweat_l * sodium_concentration.
Coefficients
| Parameter | Value | Note |
|---|---|---|
| Typical sodium in sweat | 500–1500 mg/L | |
| High-sweat athletes | >2 L/h |
Data sources
- 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. — PMID 17277604. Source of fluid-replacement and sweat-rate testing protocol.
- Baker LB. Physiology of sweat gland function: the roles of sweating and sweat composition in human health. Temperature (Austin). 2019;6(3):211-259. — PMID 31608304. Reference for the 500-1500 mg/L sweat-sodium range.
- McDermott BP, Anderson SA, Armstrong LE, et al. National Athletic Trainers' Association position statement: fluid replacement for the physically active. J Athl Train. 2017;52(9):877-895. — PMID 28985128. NATA guidance on individualized hydration.
Assumptions
- Weigh-ins are nude and dry; fluid intake during session is logged accurately.
Approximation range
Sweat rate is highly individual — repeat the test 2–3 times to establish your personal baseline.
Limitations
- Sodium concentration without a sweat-test kit is a population estimate; true value varies 3x between athletes.
- Does not model acclimatization, which can change sweat rate 20% within 10 days.
Reproducibility
Pre 80 kg, post 78.5, fluid 0.5 L, no urine, 1 h ride: sweat = (80-78.5+0.5)/1 = 2.0 L/h.
Change log
- 2026-04-24: methodology page first published.
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