Why do runners need electrolytes?

Sweat contains sodium, potassium, magnesium and chloride. Losing too many electrolytes without replacement can cause cramps, fatigue and in extreme cases hyponatraemia.

How much sodium do runners lose per hour?

The average runner loses 500-1500 mg of sodium per litre of sweat. Heavy, salty sweaters may lose even more. Sweat rate varies from 0.5 to 2.0+ litres per hour.

When should I use electrolyte tablets?

For runs over 60 minutes, especially in warm conditions. During shorter runs in cool weather, water alone is usually sufficient.

Can I have too many electrolytes?

Excess sodium is generally excreted by the kidneys, but very high intakes can cause stomach discomfort. Follow recommended dosages on electrolyte products.

RunCalcs

Electrolyte Calculator — Electrolyte Replacement for Runners

Calculate your electrolyte replacement needs based on sweat rate and conditions.

Run Duration

Body Weight

Sweat Rate

Temperature

How We Calculate This

Electrolyte Loss Estimation

Electrolyte needs are calculated from estimated sweat volume and sweat sodium concentration:

Sodium Loss (mg) = Sweat Volume (L) x Sodium Concentration (mg/L)

Sweat rates typically range from 0.5-2.0 L/hour and increase with temperature and intensity. Sodium concentration in sweat averages 700-1200 mg/L.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always consult a coach or medical professional for personalised training advice.