Daily Water Intake Calculator — How Much Water Should You Drink?
Calculate exactly how much water you should drink daily free — based on your body weight, activity level and climate. Results shown in glasses, liters and milliliters. No sign-up required.
Last updated: June 2026
Daily target
—
- In fluid ounces
- —
- Glasses (250 ml)
- —
- Bottles (500 ml)
- —
💡 Hydration tips
- Drink a glass of water as soon as you wake up.
- Carry a 1-litre bottle and aim to refill it at least once during the day.
- Check your urine colour — pale yellow usually means you're well hydrated.
Medical Disclaimer: This tool provides general health information for educational purposes only. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment.
About this tool
How much water do you really need?
The "eight glasses a day" rule is memorable but one-size-fits-all, and your real needs depend on your body and your day. This water intake calculator gives you a personalised daily target by starting from your body weight — roughly 35 ml per kilogram — and then adjusting for the factors that genuinely change how much you lose: your activity level, your climate, and whether you're pregnant or breastfeeding.
Exercise and heat are the big variables. Sweating during a workout or in hot weather can cost you hundreds of millilitres or more, so the calculator adds extra for higher activity and for hot or very hot conditions. Pregnancy and breastfeeding also raise fluid needs, and ticking that option adds an allowance. The result is shown four ways — litres, fluid ounces, 250 ml glasses and 500 ml bottles — so you can track it however you prefer to drink.
Staying well hydrated supports almost everything your body does: energy and concentration, temperature regulation, digestion, joint cushioning and healthy skin. Even mild dehydration can leave you tired, foggy or headachy, which is why a simple daily target you can actually hit is so useful. Remember that about a fifth of most people's fluid comes from food, and other drinks count too — you don't have to drink the whole figure as plain water, though water is the healthiest, calorie-free option.
This is general guidance, not medical advice — needs vary, and anyone with a kidney or heart condition should follow their doctor's fluid recommendations. The calculation runs privately in your browser. Enter your weight and habits above to get your target, and explore the calorie and BMR tools to round out your daily health numbers.
How it works
Three quick steps — no account, nothing uploaded to a server.
Enter your weight
Type your weight in kilograms or pounds.
Set activity and climate
Tell us how active you are and how warm it is.
Get your target
See litres, ounces, glasses and bottles per day.
General health information related to this tool is available from the US CDC nutrition resources. Last checked July 2026.
FAQ
Frequently asked questions
How much water should I drink a day?
A common starting point is about 35 ml of water per kilogram of body weight, which for many adults works out to roughly 2 to 3 litres a day. This calculator personalises that baseline by adding extra for your activity level, your climate, and pregnancy or breastfeeding, then shows the total in litres, fluid ounces, glasses and bottles.
Does exercise and hot weather change my needs?
Yes, significantly. Exercise increases water loss through sweat and breathing, and hot or very hot climates raise it further, so the calculator adds several hundred millilitres for higher activity and warmer conditions. On heavy training days or in extreme heat you may need even more than the estimate.
Do other drinks and food count?
Yes. Around 20% of most people's fluid intake comes from food — especially fruits, vegetables and soups — and other beverages like milk, tea and juice also contribute. The figure here is total daily fluid; you don't need to drink all of it as plain water, though water is the healthiest, calorie-free choice.
Can I drink too much water?
It's rare, but drinking very large amounts in a short time can dilute blood sodium (hyponatraemia), which is dangerous. Spread your intake through the day rather than forcing large volumes at once, and let thirst and urine colour guide you. People with kidney or heart conditions should follow their doctor's fluid advice.
Is my data private?
Yes. The calculation runs in your browser and your details are never uploaded or stored anywhere.
Related health tools
You might also need these.