Most “how much water should I drink” calculators hand you a single number with no explanation of where it came from. Ours shows the work.
Our water intake calculator starts from a commonly-used guideline of 33 ml per kilogram of body weight, and then:
- Cross-checks the math — 33 ml/kg works out to about 0.51 oz per pound, which lines up with the popular “half your body weight in ounces” rule of thumb, so you can see the two common guidelines agree.
- Adds for exercise — roughly 400 ml per 30 minutes of activity, a deliberately conservative pick inside the commonly cited 400–700 ml range.
- Adjusts for climate — a 10% bump for hot or humid conditions.
- Shows every unit at once — your target in ml, oz, and cups, regardless of which units you entered.
It’s a general estimate, not medical advice — individual needs vary by health conditions, medications, altitude, and how much you personally sweat, so treat this as a sensible starting point rather than a strict requirement.
Try it with your own numbers, and if you write about fitness or nutrition, the calculator is embeddable on your own site with one iframe.