Water Intake Calculator for Runners
How much water should runners drink? Get a personalized daily hydration target based on your mileage, body weight, and training intensity.
Runners lose significantly more fluid than the average person — typically 0.5 to 2 litres per hour of running through sweat and respiration, depending on pace, heat, and body size. Chronic mild dehydration degrades endurance performance, increases perceived effort, and raises core temperature, while overdrinking plain water on long runs can dilute sodium. This calculator gives you a daily baseline from your weight, age, sex, and training load; add roughly 400-800 ml per hour of running on top of it, and weigh yourself before and after long runs to calibrate your personal sweat rate (each kilogram lost ≈ 1 litre of fluid).
- Baseline daily target from your body weight and training intensity
- Add 400-800 ml per hour of running, more in heat above 25°C
- Long runs: weigh pre/post — 1 kg lost ≈ 1 L sweat, replace 150%
- Over 60-90 min: include electrolytes, not just plain water
Prefilled for this goal — adjust anything to match you.
Water Intake Calculator for Runners — FAQ
How much water should I drink on a 10K run?
For a 10K at moderate pace (roughly 50-70 minutes), plan 400-700 ml total: 150-250 ml about 20 minutes before, sips every 15-20 minutes during, and rehydrate afterwards. Cooler weather sits at the low end; hot and humid conditions can double sweat losses. Your urine colour by evening is the practical check — pale straw means you got it right.
Can I drink too much water while marathon training?
Yes. Hyponatremia (dangerously low blood sodium) happens when runners drink far more than they sweat out, especially in long slow events. Do not force-drink beyond thirst on runs under 90 minutes; on longer efforts, include electrolytes and keep intake roughly at or below your measured sweat rate.