Water Intake for Runners
Every kilometer is a withdrawal from your fluid account. Set your daily baseline here, then layer on your training.
Fill in your details to see your daily goal
Daily Baseline First, Then the Miles
Runners tend to obsess over race-day hydration and neglect the boring daily base — yet chronic under-drinking by even 1–2% of body water raises perceived effort, heart rate and injury risk across an entire training block. Start with the calculator above: enter your training-day mileage as exercise minutes and your season's climate. A 70 kg runner logging 45 minutes a day in temperate weather lands near 3 liters; the same runner in a southern summer pushes 3.5. That's the number your water bottles should hit before any special race strategy begins.
Race-Day Rules Worth Remembering
Drink to a plan, not to thirst alone, on runs past 90 minutes — roughly 400–800 ml per hour depending on your measured sweat rate and heat. Practice that plan on training runs well before race day, because gut tolerance is trainable. And never chase weight on the scale during a race: gaining weight mid-race means you're over-drinking, which carries its own serious risks.
Frequently Asked Questions
How much extra water should runners drink?
Beyond your daily baseline, add roughly 500 ml for every 30 minutes of running — a 60-minute easy run costs about a liter. In heat or for heavy sweaters, that can climb 30–50% higher. The calculator above handles the daily math; log your sweat rate for race precision.
How do I calculate my sweat rate?
Weigh yourself nude before and after a 1-hour run without drinking. Each kg lost ≈ 1 liter of sweat, so if you lost 0.8 kg you sweat about 800 ml/hour — replace 80–100% of that hourly rate during long efforts, plus your baseline for the rest of the day.
Should runners drink water or electrolytes?
Water for sessions under about 60–75 minutes; electrolyte drinks when you're out longer or sweating heavily, since replacing fluid without sodium risks diluting blood sodium. See our electrolytes guide for how much sodium per liter of fluid is worth targeting.
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