Based on your weight
Uses a practical baseline of about 35 ml per kilogram, then adds extra for the exercise you do.
CalculatorsRuns in your browser
Water Intake Calculator
A daily hydration target from your weight and how much you exercise.
- Input
- No upload needed — instant
- Privacy
- Nothing is uploaded
- Cost
- Free · no sign-up · no watermark
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Overview
About the Water Intake Calculator
Estimate how much water to drink each day from your weight and exercise, shown in litres, millilitres, cups and fluid ounces, using a per-kilogram baseline.
How much water you need depends mostly on your body size and how much you sweat. This calculator estimates a daily target from your weight and exercise, then shows it in litres, millilitres, US cups and fluid ounces so it maps onto whatever bottle or app you use.
The estimate
baseline = weight(kg) × 35 ml
exercise = (minutes ÷ 30) × 350 ml
daily = baseline + exerciseThe 35 ml-per-kg baseline is a practical middle ground; the exercise term replaces sweat losses.
Use it as a guide, not a rule
About a fifth of your water comes from food, and heat, altitude, illness, pregnancy and breastfeeding all raise your needs. The most reliable signals are thirst and pale-yellow urine.
Private and precise
This calculator produces estimates from published formulas and is not medical advice. For anything about your health, talk to a doctor or a registered dietitian.
Step by step
How to use the Water Intake Calculator
Choose your units and enter your weight.
Add how many minutes of exercise you do in a typical day.
Read your daily water target in litres, cups and fluid ounces.
Why use it
Benefits and common use cases
What this tool is good for, and what it deliberately does not try to do.
Every unit you want
The same target shown in litres, millilitres, US cups and fluid ounces, so it fits any bottle or tracker.
Accounts for exercise
Adds roughly 350 ml for every 30 minutes of activity, since sweat replaces what a sedentary estimate misses.
Questions
Frequently asked questions
Short, honest answers about quality, limits and privacy.
How much water should I drink a day?
A common guide is about 35 ml per kilogram of body weight, plus extra for exercise, heat and illness. For a 70 kg person that is roughly 2.4 litres before activity. Needs vary, so use thirst and pale urine as your real check.
Does coffee and food count?
Yes. Around 20% of daily water typically comes from food, and drinks like tea and coffee contribute too, despite their mild diuretic effect. Plain water should still make up most of it.
Can I drink too much water?
Yes, though it is rare. Extremely high intake in a short time can dilute blood sodium (hyponatremia). Spreading water across the day and drinking to thirst avoids this.