Water Intake Calculator
Calculate personalized daily water intake targets based on weight, activity level, climate, and health status with practical cup and bottle counts.
Unit system
Daily water target
2.5 L
2,450 ml / 82.9 oz
Cups (8 oz)
10.4
standard cups per day
500 ml bottles
4.9
standard bottles per day
1 L bottles
2.5
large bottles per day
Hourly target
153 ml
based on 16 waking hours
Factor breakdown
| Factor | Amount |
|---|---|
| Base (weight x 35 ml/kg) | 2,450 ml |
| Sex adjustment (x 1.0) | 2,450 ml |
| Activity | +0 ml |
| Climate | +0 ml |
| Total | 2,450 ml |
This calculator provides estimates based on general guidelines. Individual hydration needs vary with diet, medications, health conditions, altitude, and other factors. Consult a healthcare provider for personalized recommendations. Not medical advice.
How this tool works
This calculator estimates your daily water intake using a weight-based formula (35 ml per kilogram of bodyweight) recommended by EFSA and Mayo Clinic guidelines. It then adjusts for activity level, climate, sex, and special conditions like pregnancy or breastfeeding. The sex adjustment applies a 0.85 factor for females to reflect average lower body mass ratios. Activity additions range from 0 ml (sedentary) to 1,000 ml (athlete), and climate additions range from 0 ml (temperate) to 500 ml (very hot). Pregnancy adds 300 ml and breastfeeding adds 700 ml per ACOG recommendations. Results are converted into practical units: cups (8 oz), 500 ml bottles, liters, and fluid ounces, plus an hourly target based on 16 waking hours.
Worked example
A 70 kg male who is very active and lives in a hot climate: base intake is 70 x 35 = 2,450 ml. Very active adds 700 ml and hot climate adds 250 ml, giving a total of 3,400 ml per day. That is about 3.4 liters, 14.4 cups (8 oz), 6.8 bottles (500 ml), or 115 fluid ounces. Spread over 16 waking hours, that is roughly 213 ml per hour, or about one glass every 45 minutes.
Frequently asked questions
How much water should I drink per day?
A common starting point is 35 ml per kilogram of bodyweight, but actual needs vary with activity level, climate, diet, and health status. The "8 glasses a day" rule is a rough heuristic; use this calculator for a personalized estimate.
Does coffee or tea count toward hydration?
Moderate amounts of caffeinated drinks contribute to hydration despite mild diuretic effects. However, they should supplement, not replace, plain water consumption.
Can you drink too much water?
Yes. Hyponatremia (water intoxication) can occur when extreme amounts of water are consumed in a short period, diluting blood sodium. For endurance athletes, over-hydrating during events is a real risk. The targets in this calculator represent daily totals, not single-session amounts.
Does exercise increase my water needs?
Yes. You lose roughly 0.5-1 litre of water per hour of moderate exercise through sweat and breathing. In hot or humid conditions the loss is higher. Add fluid during and after exercise on top of your baseline daily target.