Water Intake Calculator
Daily fluid needs scale with body size, sweat losses, and heat. A common working estimate is about 35 ml of water per kilogram of body weight, plus roughly 500 ml for every 30 minutes of exercise, raised by about 15% in hot or humid conditions.
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Daily water target
2.95 L
Cups (240 ml)
12.3 cups
Details
Updates as you typeMinutes of moderate-to-hard activity on a typical day.
Summary
Daily water target
2.95 L
Daily water target
2.95 L
- Baseline need2.45 L83%
- Exercise allowance0.50 L17%
- Climate adjustment0.00 L0%
- Millilitres
- 2,950 ml
- Cups (240 ml)
- 12.3 cups
- Glasses (250 ml)
- 11.8 glasses
- This is total fluid from all sources. Food supplies roughly 20% of it, so the amount you actually need to drink is usually a little lower.
- Kidney disease, heart failure, pregnancy, breastfeeding, and some medications all change fluid needs. Ask a clinician before using a fixed target.
- Thirst and pale-straw urine remain the most practical day-to-day guides; drinking far beyond need can dilute blood sodium, which is dangerous.
How this is calculated
- Body weight
- 70.0 kg
- Baseline at 35 ml/kg
- 2,450 ml
- Exercise replacement (500 ml per 30 min)
- 500 ml
- Climate multiplier
- 1.00 ×
- Total fluid target
- 2,950 ml
- Added by the climate
- 0 ml
Compare scenarios
See how one change moves the result
- CurrentYour inputs as they stand2.95 LCurrent
- Body weightkg 87.53.56 L
- Exercisemin/day 403.12 L
For informational purposes only. This is not medical advice — consult a healthcare professional about your health.
Frequently asked questions
How much water should I drink a day?
For most healthy adults, about 35 ml per kilogram of body weight is a reasonable baseline — roughly 2.5 litres for a 70 kg person — plus around 500 ml for every 30 minutes of exercise. Hot or humid conditions push that higher still.
Does the eight-glasses-a-day rule hold up?
It is a rough memory aid rather than a finding. Eight 250 ml glasses is two litres, which lands near the baseline for a smaller adult but understates the need of a large or very active person and overstates it for a small sedentary one.
Do coffee, tea, and food count toward the total?
Yes. Caffeinated drinks are mildly diuretic but still contribute net fluid, and food supplies roughly 20% of total intake — more if you eat a lot of fruit, vegetables, soup, or yoghurt. This calculator reports total fluid from all sources.
Can you drink too much water?
You can. Drinking far more than the kidneys can excrete dilutes blood sodium, a condition called hyponatraemia, which causes headache, nausea, confusion, and in severe cases seizures. Endurance athletes who over-drink plain water are most at risk.
How can I tell if I am drinking enough?
Urine colour is the simplest check: pale straw suggests adequate hydration, while dark yellow or amber suggests you are behind. Persistent thirst, dry mouth, headache, and low energy are other common signals of a shortfall.