Water intake calculator
A personalised daily fluid target from your bodyweight and how much you train — in ounces, cups and litres, with the caveats most water calculators skip.
How it's estimated
We start from a baseline of about 35 mL of fluid per kg of bodyweight — the figure commonly used for healthy adults — then add roughly 500 mL per hour of exercise and a little extra for hot or humid conditions. The result is a total daily fluid target, not just plain water.
- Coffee, tea, milk and most drinks count toward it.
- Watery foods — fruit, vegetables, soup, yogurt — count too.
- The easiest check that you're on track: pale-straw urine colour.
Useful next steps
Frequently Asked Questions
How much water should I drink a day?
A common evidence-based baseline is about 30–35 mL of fluid per kilogram of bodyweight, plus roughly 350–700 mL extra per hour of exercise. For many adults that lands near the familiar 2–3 litres (8–12 cups) a day — but it scales with your size, activity, heat and diet.
Does all of it have to be plain water?
No. Most of your fluid can come from water, but coffee, tea, milk and watery foods (fruit, vegetables, soup, yogurt) all count toward the total. The number here is total fluid; plain water just makes hitting it easy and calorie-free.
Is the "8 glasses a day" rule real?
It is a rough rule of thumb, not a law. Eight 8 oz glasses is about 1.9 L, which is in the right ballpark for an average adult — but your actual need depends on bodyweight, activity, climate and health. This calculator personalises it to you.
How do I know if I am drinking enough?
The simplest real-world check is urine colour — pale straw is well hydrated, dark yellow means drink more. Thirst is also a reasonable guide for healthy adults. Needs rise in heat, at altitude, when ill, and during pregnancy or breastfeeding.
Can you drink too much water?
Rarely, but yes — drinking extreme amounts very quickly can dangerously dilute blood sodium (hyponatremia). The targets here are daily totals spread across the day, not amounts to drink at once.
General educational information, not medical advice. Fluid needs rise with heat, altitude, illness, pregnancy and breastfeeding — check with a clinician if you have a heart or kidney condition that limits fluids.