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Water Intake Calculator

Estimate how much water you should drink each day from your weight. Enter your weight and this free water intake calculator shows your target in litres and in glasses — a quick, sensible starting point that you can adjust for activity, weather and diet.

Weight (kg)

2.31 L

What is a water intake calculator?

A water intake calculator estimates how much fluid you should drink in a day, most often from your body weight. A widely used rule of thumb is to multiply your weight in kilograms by about 0.033 to get litres per day — so a 70kg person targets around 2.31 litres, or roughly nine standard glasses. It turns a vague 'drink more water' into a concrete daily goal.

Your true need depends on more than weight. Exercise, hot weather, illness, pregnancy and a diet high in salty or diuretic foods all raise how much you should drink, while water in food and drinks such as tea and coffee counts toward the total. The estimate is a baseline to adjust from, not a precise medical prescription.

This calculator runs in your browser, so it is quick and private whenever you want a number to aim for.

How to use the water intake calculator

Enter your body weight in kilograms.
Click Calculate to estimate your daily target.
Read the result in litres and in glasses, then adjust for activity and weather.

Example

Enter a weight of 70kg. The calculator shows about 2.31 litres per day — roughly 9 glasses of 250ml — worked out as 70 × 0.033. Enter 60kg instead and the target is about 1.98 litres, or around 8 glasses.

Who is this water intake calculator for?

Your daily water target scales with body weight, so the estimate differs by body size and situation. This calculator gives a useful baseline for men and women, seniors and teens alike — just adjust for the factors below.

Men: a typical 75kg man targets about 2.5 litres a day (≈ 10 glasses), rising with exercise.
Women: a typical 65kg woman targets about 2.1 litres a day (≈ 9 glasses), and slightly more during pregnancy or breastfeeding.
Seniors: the thirst sense weakens with age, so an older adult often needs to budget water deliberately rather than wait for thirst.
Teens: growing teens need steady hydration through school and sport; a 50kg teen targets about 1.65 litres a day.
Active adults: add roughly 500ml–1 litre for a workout, and more on hot or humid days.

Water intake by weight

The table below shows the daily estimate from the common weight × 0.033 rule, in litres and in standard 250ml glasses.

Weight (kg)	Litres/day	Glasses (250ml)
50	1.65	7
60	1.98	8
70	2.31	9
80	2.64	11
90	2.97	12

Common use cases

Setting a daily hydration goal after starting a fitness or diet plan.
Planning water intake for a hot day, a workout or long travel.
Tracking whether you're drinking enough as part of a wellness routine.
Reminding yourself to drink regularly when your schedule is busy.

Pro tips

Add roughly 500ml–1 litre for a workout and more on a hot or humid day.
Sip over the day rather than chugging; steady hydration beats large single doses.
Include water-rich foods and teas — they count toward your total fluid.
Your urine can be a handy guide: pale straw usually means you're well hydrated.

FAQ

How much water should I drink a day?

A common baseline is about 2–2.5 litres for an average adult. Multiply your weight in kg by roughly 0.033 to personalise the estimate.

How is water intake calculated?

The estimate multiplies your weight in kilograms by about 0.033 to give litres per day, then converts that into 250ml glasses.

Does activity or weather matter?

Yes. Exercise, heat and humidity all increase fluid loss, so you should drink more on those days.

Is more water always better?

No. Drinking far more than you need can strain your kidneys. Stick close to your target and adjust gently.

Do tea, coffee and food count?

Yes. Most fluids and water-rich foods count toward your daily total, though caffeinated drinks contribute slightly less.

Is this calculator free?

Yes, it is free with no signup, and it runs entirely in your browser.

Should I drink more when pregnant?

It is a common recommendation to increase fluid intake during pregnancy, but check the exact amount with your doctor.

Is the result a medical recommendation?

No. It is a general estimate for healthy adults — consult a health professional for personalised advice.

Is 250ml one glass?

The calculator uses a standard 250ml serving, which is a typical glass size in many countries.