How much should I drink when running?

Aim for 400-800 ml per hour of running, depending on temperature and sweat rate. Drink to thirst rather than forcing fluid intake.

Should I drink water or sports drink?

For runs under 60 minutes, water is sufficient. For longer runs, a sports drink with electrolytes and carbohydrates helps maintain performance.

How do I know if I am dehydrated?

Check your urine colour — pale yellow is well-hydrated. Dark yellow or amber suggests dehydration. Weigh yourself before and after running to estimate fluid loss.

RunCalcs

Hydration Calculator — Running Fluid Needs

Calculate how much fluid you need before, during and after running.

Body Weight

Duration

Temperature

How We Calculate This

Hydration Calculation

Sweat rate varies by weight, temperature, and intensity. The calculator estimates fluid needs based on typical sweat rates adjusted for conditions.

Pre-run: 5 ml per kg body weight, 2-3 hours before

During: 400-800 ml per hour

Post-run: 150% of fluid lost during exercise

Frequently Asked Questions

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Electrolyte Calculator

Calculate electrolyte replacement needs based on sweat rate.

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Calculate how many energy gels you need for your race distance.

Last updated: February 2026

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