Water intake calculator

It depends on your weight, activity and climate. With the formula Waltermelon uses, a 160 lb woman who works out 1-2 times a week in a temperate climate should aim for about 84.5 oz (2.5 liters) a day, about 10.5 cups. A 180 lb man with the same routine lands at about 104.8 oz (3.1 liters). Enter your own numbers in the calculator above for your goal.

Multiply your weight in kilograms by 35 ml, or your weight in pounds by a little over half an ounce. Women take 90% of that, adults 65 or older take 90% too, and both apply to a woman 65 or older. Then add about 7 oz for 1-2 workouts a week or 13.5 oz for 3 or more, and 8.5-17 oz for warm or hot weather. Cold weather adds about 3.4 oz. If you’re pregnant, add about 12 oz, or about 24 oz while breastfeeding. Finally, round the total to the nearest 100 ml (about 3.4 oz). Waltermelon uses exactly these steps to set your daily goal.

Most adults land between about 60 and 120 oz a day. With the Waltermelon formula, a 150 lb woman who rarely works out needs about 71 oz in a temperate climate, and a 150 lb man about 81 oz. More activity and heat push it higher: a 200 lb man who works out 3 or more times a week in hot, humid weather needs about 139 oz.

It’s a common rule of thumb with no official basis, but it lands close to how Waltermelon starts: a little over half an ounce per pound. The difference is that Waltermelon then adjusts for sex, age, activity, climate and pregnancy. Half your body weight gives a 150 lb person 75 oz, while the Waltermelon formula gives a 150 lb woman who rarely works out about 71 oz and a 150 lb man who works out 3 or more times a week about 95 oz.

For many adults it’s about 8 to 15 cups of 8 oz each. A 150 lb woman with little exercise needs about 9 cups by the Waltermelon formula, and a 175 lb man who works out 3 or more times a week about 13.5 cups. The calculator above shows your number in both ounces and cups.

Yes. Coffee and tea are mostly water and count toward your fluids. In Waltermelon, coffee and tea are built in and free, each with its own hydration value, and the app adds up your caffeine too. Our article on whether coffee counts as water intake goes into the details.

The Waltermelon formula adds about 7 oz (200 ml) for 1-2 workouts a week and about 13.5 oz (400 ml) for 3 or more. Warm weather adds about 8.5 oz (250 ml) and hot, humid weather about 17 oz (500 ml). On a long or very sweaty workout day you may need more, so drink to thirst as well.

It gives a general estimate only. It adds about 12 oz (350 ml) for pregnancy and about 24 oz (700 ml) for breastfeeding, the same as the Waltermelon app, but your doctor should confirm your goal. If you have kidney disease, heart failure or another condition that limits fluids, follow your doctor’s advice instead of any calculator.

Yes. This calculator runs the same formula Waltermelon uses when you set up the app, from your weight, sex, age, activity and climate, rounded to the nearest 100 ml. The only difference is age: the app asks your exact age, while this page only asks whether you’re 65 or older, which gives the same result for adults.

Spread it over your waking hours instead of catching up at night. Waltermelon sends reminders every 30 minutes to every 3 hours, only between your wake-up time and bedtime, lets you log a drink with one tap from a home screen widget, and keeps a streak going as long as you hit your goal.