💧 Water Intake Calculator
Estimate your daily water needs from your weight, exercise and climate.
Quick answer: A common guide is 35 ml of water per kg of body weight plus about 12 ml per minute of exercise. A 70 kg person who exercises 30 minutes a day in a temperate climate needs about 2.8 L (95 fl oz) a day.
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Water Intake Calculator inputs
Result
Drink about
2.8 L/day
≈ 11.9 cups (8 fl oz) a day
| Body weight | 2.45 L |
| Exercise | 0.36 L |
| Hot climate | 0 L |
| Total | 2.81 L |
- Litres
- 2.8 L
- US cups
- 11.9
- Fluid ounces
- 95 oz
How daily water needs are estimated
Water needs scale with body size, then rise with sweat losses from exercise and heat. This calculator uses a widely used weight-based baseline with simple add-ons.
Water (ml) = 35 × weight(kg) + 12 × exercise minutes + 500 (hot or humid climate)
1 litre ≈ 33.8 US fl oz ≈ 4.2 US cups (8 fl oz each).
Worked example
A 70 kg adult who exercises 30 minutes a day in a temperate climate: 35 × 70 = 2,450 ml, plus 12 × 30 = 360 ml for exercise, totals 2,810 ml ≈ 2.8 L – about 95 fl oz or 11.9 cups. In hot weather add another 500 ml for 3.3 L.
Reference intakes
| Source | Women | Men |
|---|---|---|
| US National Academies (total water, food + drink) | 2.7 L/day | 3.7 L/day |
| European Food Safety Authority (total water) | 2.0 L/day | 2.5 L/day |
These totals include water from food, so the amount you drink is usually a little lower.
Hydration tips
- Start the day with a glass of water and keep a refillable bottle nearby.
- Drink 400–600 ml in the two hours before a workout and sip during long sessions.
- Increase intake during illness with fever, vomiting or diarrhoea, and when breastfeeding.
- People with heart or kidney conditions may need to limit fluids – follow medical advice.
Why water needs differ
Larger bodies hold and lose more water, and every hour of sweaty exercise can cost 0.5–1 litre or more. Heat, humidity, altitude and dry indoor air increase losses further, while cool weather and a diet rich in fruit and vegetables reduce the amount you need to drink.
For general information only – not medical advice. Consult a healthcare professional.
Frequently asked questions
Is 8 glasses a day enough?
Eight 8-oz glasses (about 1.9 L) is a reasonable minimum for smaller, less active adults, but larger or more active people usually need more. A weight-based estimate is more personal.
Does coffee or tea count?
Yes. Tea, coffee, milk and other drinks all count toward fluid intake, and roughly 20% of daily water typically comes from food such as fruit, vegetables and soups.
How can I tell if I am drinking enough?
Pale-yellow urine and rarely feeling thirsty are good signs. Dark urine, headaches, fatigue and dizziness can signal dehydration.
Can you drink too much water?
Yes. Drinking very large amounts quickly, especially during long endurance events, can dilute blood sodium (hyponatremia). Spread intake through the day and use electrolytes for long, sweaty sessions.