Water Intake Calculator
Estimate how much water to drink each day from your body weight and exercise time, a practical baseline in litres or ounces. Calculates privately in your browser.
Daily water target
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Show the math
A baseline from body weight plus a top-up for exercise:
water = 35 ml × kg + 350 ml per 30 min of exercise
About 20% of your fluid usually comes from food, so this is a total target, not what you must drink. Hot weather, altitude, illness, and pregnancy raise your needs, let thirst and urine colour guide you day to day.
What this does
A water intake calculator estimates how much water to drink each day from your body weight and exercise time, giving a practical baseline in litres or ounces.
How it works
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 to replace what you sweat out.
How to use it
- Enter your body weight.
- Enter your daily exercise time.
- Choose litres or ounces.
- Read your estimated daily water target.
Understanding your result
You typically get around 20% of your fluid from food, so this total is a guide. Hot weather, altitude, illness, pregnancy, and breastfeeding raise your needs, use thirst and urine colour as everyday cues.
Example
A 70 kg person doing 30 minutes of exercise has a baseline near 2.45 L plus about 0.35 L, roughly 2.8 L for the day.
Sources & methodology
- CDC, Water and Healthier Drinks, Daily hydration guidance
Last updated .
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 to replace what you sweat out.
Does food count toward this?
Yes, you typically get around 20% of your fluid from food. This figure is a total target; drinking a bit less and eating water-rich foods can still get you there.
Do I need more in some situations?
Yes. Hot weather, high altitude, illness, pregnancy, and breastfeeding all raise your needs. Use thirst and urine colour as everyday guides.
Is my data stored?
No. All calculations happen locally in your browser.
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