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Water Intake Calculator

Estimate how much water to drink each day based on your body weight and how much you exercise.

Water Intake Calculator

🔒 Nothing you enter is sent anywhere or stored. All processing happens in your browser.

How it works

A common, easy-to-remember guideline is to drink roughly 35 millilitres of water per kilogram of body weight each day. This calculator applies that baseline to your weight, then adds extra to cover fluid lost through exercise — about 350 ml for each 30 minutes of activity, since sweating raises your needs.

The result is shown three ways — litres, cups (using a 240 ml cup) and millilitres — so you can track it however suits you. The exercise contribution is listed separately so you can see how much of your target comes from staying active.

These are general targets for a healthy adult in a temperate climate. You'll need more in hot weather, at altitude, when ill, or if pregnant or breastfeeding, and remember that food and other drinks contribute fluid too. Anyone with kidney, heart or other conditions should follow their doctor's advice. The calculation runs entirely in your browser.

Examples

70 kg, 30 min exercise → about 2.8 L (roughly 12 cups) per day.
90 kg, no exercise → around 3.2 L as a baseline target.
55 kg, 60 min exercise → about 2.6 L including the workout top-up.

Frequently asked questions

How is the target calculated?
It uses about 35 ml of water per kilogram of body weight as a baseline, then adds roughly 350 ml for every 30 minutes of exercise you enter.
Does food and other drinks count?
Yes. Around a fifth of most people's fluid comes from food, and tea, coffee and juice also contribute, so you may not need to drink the full figure as plain water.
Should I drink more in hot weather?
Yes. Heat, humidity, altitude, illness, pregnancy and breastfeeding all increase your needs beyond this general estimate.
Can you drink too much water?
Very rarely, but drinking extreme amounts in a short time can be dangerous. Spread intake across the day and let thirst guide you.
Is my information private?
Yes. Everything is calculated in your browser and nothing you enter is stored or uploaded.