Understanding This Calculator
Hydration needs scale with body size and activity level. This calculator uses the commonly cited baseline of 33 ml of water per kilogram of body weight per day, then adds roughly 400ml for every 30 minutes of exercise to replace sweat losses.
Climate, altitude, and individual sweat rate all shift actual needs — treat this as a starting point and adjust based on urine color (pale yellow is the target) and thirst.
- kg body weight in kilograms
- 0.033 L baseline per kg per day
- 0.4 L added per 30 min of exercise
| Weight | Daily Target |
|---|---|
| 130 lb (59 kg) | 1.9 L |
| 165 lb (75 kg) | 2.5 L |
| 200 lb (91 kg) | 3.0 L |
Frequently Asked Questions
Does coffee or tea count toward water intake?
Caffeinated beverages contribute to hydration despite a mild diuretic effect — the net fluid contribution is still positive, but plain water remains the best primary source.
Can I drink too much water?
Yes — very rarely, extreme overconsumption in a short window can cause hyponatremia (diluted blood sodium). It’s a real risk mainly for endurance athletes drinking multiple liters per hour without electrolytes.