Water Intake Calculator
Enter your weight, activity level and climate to estimate how much water to drink each day, shown in liters, US fluid ounces, cups and 500 ml bottles, with an hour-by-hour drinking plan.
Hourly drinking schedule
| Time | Drink | Running total |
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This is an estimate for healthy adults. Needs vary with health, medication and sweat rate; people with heart or kidney conditions should follow their doctor's advice.
How to use the Water Intake Calculator
- Enter your body weight and choose kg or lb.
- Pick your activity level, or choose to enter your daily exercise minutes yourself.
- Select your climate and, if it applies, pregnancy or breastfeeding.
- Press Calculate to see your daily target in liters, ounces, cups and bottles.
- Set your wake-up time and bedtime to get an hourly drinking schedule.
How the water intake formula works
The calculator builds your daily estimate in steps:
- Base need = body weight (kg) × 35 ml
- Exercise = 350 ml for every 30 minutes of activity per day
- Climate = (base + exercise) × 0%, 10%, 20% or 30%
- Pregnancy +300 ml or breastfeeding +700 ml
- Optionally, subtract 20% that typically comes from food
Example: a 70 kg person who exercises 45 minutes a day in a temperate climate. Base: 70 × 35 = 2,450 ml. Exercise: 45 ÷ 30 × 350 = 525 ml. Climate: (2,450 + 525) × 10% = 297.5 ml. Total ≈ 3,270 ml, or about 3.3 liters (about 111 US fl oz, about 13.8 cups). If 20% comes from food, the amount to drink is about 2.6 liters.
Water intake by body weight
| Weight | Base need | US fl oz | Cups (8 oz) | With 30 min exercise |
|---|---|---|---|---|
| 50 kg (110 lb) | 1.75 L | 59 | 7.4 | 2.10 L |
| 60 kg (132 lb) | 2.10 L | 71 | 8.9 | 2.45 L |
| 70 kg (154 lb) | 2.45 L | 83 | 10.4 | 2.80 L |
| 80 kg (176 lb) | 2.80 L | 95 | 11.8 | 3.15 L |
| 90 kg (198 lb) | 3.15 L | 107 | 13.3 | 3.50 L |
| 100 kg (220 lb) | 3.50 L | 118 | 14.8 | 3.85 L |
Values are before any climate adjustment. For comparison, the US National Academies suggest a total fluid intake of about 3.7 L a day for men and 2.7 L for women, including water from food.
Signs you may need more water
Thirst is a good guide for most healthy adults. Pale yellow urine usually means you are well hydrated, while dark yellow urine, headaches, tiredness and dizziness can be signs of dehydration. You need more fluid in hot weather, at high altitude, during illness with fever, vomiting or diarrhea, and during long workouts.
Frequently asked questions
How much water should I drink a day?
A common rule of thumb is about 35 ml of fluid per kilogram of body weight, which is around 2.5 liters for a 70 kg adult, plus more for exercise and hot weather. The calculator adds those adjustments for you.
Does the result include water from food?
By default the result is your total fluid need. Food such as fruit, vegetables and soup usually supplies about 20% of daily water, so tick the food option to see only the amount you need to drink.
How much extra water do I need when I exercise?
Roughly 350 ml (about 12 oz) for every 30 minutes of exercise, more in heat or if you sweat heavily. Long or intense sessions may also need electrolytes.
How much water should I drink when pregnant or breastfeeding?
Health authorities suggest about 300 ml extra per day during pregnancy and about 700 ml extra while breastfeeding, on top of your usual needs.
Do coffee and tea count toward water intake?
Yes. Coffee, tea, milk and other drinks all count toward your fluid intake. Moderate caffeine has only a mild diuretic effect, though plain water is the best everyday choice.
Can you drink too much water?
Yes. Drinking very large amounts in a short time can lower blood sodium (hyponatremia). Spread your intake through the day and do not force down much more than you need. People with heart or kidney conditions should follow medical advice.