The full tool
Water Intake Calculator
Quick answer
This water intake calculator estimates your daily drinking goal from your weight, activity, and climate. As a rule of thumb, aim for 30–35 ml per kg of body weight (about half an ounce per pound) — roughly 2–3 litres for most adults — and add more for exercise, heat, pregnancy, or illness.
Fine-tune
Your daily goal
of water a day · about 10.5 glasses or 5 half-litre bottles
- 2.6
- Litres
- 88
- Ounces
- 10.5
- Glasses
Pace yourself
Spread it across the day and ease off after 9:00 PM for better sleep.
Electrolytes? Not needed
For everyday hydration, plain water and a normal diet cover your electrolytes just fine.
A friendly estimate for healthy adults, not medical advice. Your needs rise with heat, exercise, illness, pregnancy, and some medications. Don't drink more than ~1 litre per hour.
How much water do you really need?
There is no single magic number. Your body loses water through urine, sweat, breathing, and digestion, and how much you need back depends on your size, how active you are, and the weather where you live. The formula behind this calculator turns those factors into a practical daily target.
Hydration scientists at the U.S. National Academies put adequate total water intake at about 3.7 litres a day for men and 2.7 litres for women — but that figure includes the water in your food. Since roughly a fifth of your fluid comes from meals, your drinking goal is a little lower, which is what we show.
Reading your result
- Litres & ounces — your headline daily goal, the amount to drink across the day.
- Glasses & bottles— the same goal in everyday containers, so it's easy to track.
- Electrolytes verdict— whether a daily electrolyte top-up is genuinely worth it for your profile (for most people, it isn't).
- Pace & stop-time — front-load earlier in the day and ease off before bed to sleep better.
Frequently asked
How does this water intake calculator work?
It starts from about 33 ml of water per kilogram of body weight, adds fluid for your activity level, adjusts for climate, and applies higher floors for pregnancy, breastfeeding, or GLP-1 medication. The result is your daily drinking goal in litres, ounces, glasses, and bottles.
Is a water intake calculator accurate?
It gives a well-grounded estimate, not a precise prescription. Real needs vary day to day with heat, exercise, illness, and diet. Use the number as a target and let thirst and pale-yellow urine fine-tune it.
How much water should I drink based on my weight?
A common rule is half to three-quarters of an ounce per pound of body weight (about 30–40 ml per kg). For a 150 lb (68 kg) adult that's roughly 75–113 oz, or about 2.2–3.3 litres a day.
Should I count coffee, tea, and food?
Yes. Coffee and tea count as fluid, and food adds roughly 20% of your total water on top of what you drink. This calculator targets your drinking goal, so food is a helpful bonus rather than something to subtract.
Sources
- 1.U.S. National Academies (IOM/NAM), 2005 — Adequate total water intake of about 3.7 L/day for men and 2.7 L/day for women, including water from food and all beverages.
- 2.European Food Safety Authority (EFSA), 2010 — Adequate total water intake of 2.5 L/day for men and 2.0 L/day for women under temperate conditions.
- 3.Mayo Clinic — General guidance of roughly 2.7–3.7 L of total fluids a day, with thirst and pale-yellow urine as everyday checks.
- 4.U.S. Geological Survey (USGS) — The human body is about 60% water by weight.