Water Intake Calculator Calculators
A daily hydration target based on weight, activity and climate.
Water Intake Calculator is a free online tool that a daily hydration target based on weight, activity and climate. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 3
- Works offline
- Yes, after the first visit
About Water Intake Calculator
The commonly repeated "eight glasses a day" has no strong evidence behind it. This estimate scales with bodyweight, exercise and climate, which at least reflects the actual drivers. Food contributes roughly 20% of intake, and thirst is a reasonably good regulator for most healthy adults.
How to use it
- Enter weight (kg), exercise (minutes/day) and climate.
- Results update the moment anything changes.
The 3 settings
| Setting | What it does | Default |
|---|---|---|
| Weight (kg) | A numeric value. | 70 |
| Exercise (minutes/day) | Range 0–600. | 30 |
| Climate | Choose from 4: Cool, Temperate, Warm, Hot / humid. | Temperate |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Weight (kg), Exercise (minutes/day), Climate |
Questions
Can I drink too much water?
Yes. Hyponatraemia — dangerously diluted blood sodium — is rare but real, and has killed endurance athletes and participants in drinking contests. Very large volumes in a short period are the risk, not steady intake.
What does the climate option change?
It offers 4 choices — Cool, Temperate, Warm and Hot / humid. The default is Temperate, which suits most cases; change it when your input or your destination calls for something specific.
What are the limits on exercise (minutes/day)?
It accepts 0 to 600, starting at 30.
Is the arithmetic exact?
It uses double-precision floating point — about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.