Electrolyte & hydration loss

Based on Baker LB 2017
Barnes et al. 2019 · n=1303

This calculator estimates only the sweat losses of sodium and water during exercise. It does not assume you are taking gels, food or sports drinks — and it does not say you must take supplements either. The result tells you what your body would lose without intake; whether replacement is essential, recommended, optional or unnecessary depends on duration, intensity and conditions, and your body's own reserves.

Sport01 / 08
Surface
Discipline
Level02 / 08
Body weight03 / 08
70kg
40 kg120 kg
Duration04 / 08
2.0hours
0.5 h12 h
Distance05 / 08
20km
2 km250 km
Average pace · 10.0 km/h
Ambient temperature06 / 08
22°C
−5 °C45 °C
Total elevation gain07 / 08
meters
0 m (flat)up to 10,000 m
Intensity zone08 / 08
Z3 — Tempo. Sustained pace, short sentences. 76–90 % HRmax.
Advanced optional parameters
50%
No
L/h

Legal & methodological notice

This calculator estimates only sweat losses based on Baker LB (Sports Medicine, 2017) and Barnes et al. (Journal of Sports Sciences, 2019, n=1303 athletes). Output represents only sweat sodium and water that the body loses, assuming no intake of food, gels, sports drinks or other sodium sources during the activity.

If you consume gels, bars, bananas, salty snacks or isotonic drinks, you must subtract the sodium those provide from the total. Sodium and water values are shown as intervals to reflect interindividual variability (±25 %). The capsule recommendation is calculated on the lower bound of sodium loss to minimize hyponatremia and GI risk. The 3IE-AHCD 2015 consensus recommends drinking to thirst rather than forcing intake.

Real sweat and sodium rates vary significantly between individuals. For long sessions, competition, extreme conditions or if you have hypertension, kidney disease, heart conditions or pregnancy, consult a sports physician or qualified nutritionist.

This calculator does not constitute medical advice.

References: Baker LB. Sports Med 2017;47(Suppl 1):111-128 · Barnes KA et al. J Sports Sci 2019;37(20):2356-2366 · 3rd Intl. EAH Consensus 2015