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- A simple daily goal is half an ounce of water per pound of body weight.
- Add 12 ounces for every 30 minutes of exercise, and a little more in hot weather.
- A 160 lb person who exercises 30 minutes needs about 92 oz, or 2.7 liters.
- Coffee, tea, milk and food all count toward your total.
How to use the water intake calculator
Enter your weight
Choose pounds or kilograms and type your weight.
Add your exercise
Enter the minutes of exercise or hard physical work on a usual day.
Pick the weather
Choose mild, or hot or humid if you sweat a lot where you live.
Read your goal
You get ounces, liters, cups and bottles per day, plus a simple plan for the day. Open More options if you are pregnant or breastfeeding.
How much water should I drink a day?
There is no single number that fits everyone. Body size, activity, climate and health all change how much fluid you lose. This calculator uses a common rule of thumb that is easy to remember and adjusts for the main things that matter.
Water intake formula
Base = body weight in pounds × 0.5 oz
Exercise = minutes of exercise ÷ 30 × 12 oz
Hot weather = add 15% to the total
Daily goal = base + exercise (+ hot weather)
To convert, 1 liter is 33.8 ounces and 1 cup is 8 ounces.
Worked examples
160 lb, 30 minutes of exercise, mild weather
160 × 0.5 = 80 oz, plus 12 oz for exercise.
About 6 bottles of 16.9 oz.
200 lb, 60 minutes of exercise, hot weather
200 × 0.5 = 100 oz, plus 24 oz for exercise, then 15% more.
Heavy exercise in the heat raises needs a lot.
130 lb, no exercise, mild weather
130 × 0.5 = 65 oz.
A person who is not active needs less.
Water goal by body weight
No exercise, mild weather
Half an ounce per pound.
Add 12 oz for each 30 minutes of exercise.
Where a water intake calculator helps
Daily habit
Set a clear goal and track it with a bottle.
Workouts
See how exercise changes what you need.
Hot days
Plan for extra fluid in summer heat.
Pregnancy and nursing
See a small allowance in the advanced options.
This is a general estimate, not medical advice. Kidney, heart and liver conditions, and some medicines, can change how much fluid is safe. Ask your doctor if you have a medical condition. Drinking very large amounts in a short time can be harmful, so spread your water through the day.
Water intake calculator FAQ
How much water should I drink a day?
A common rule is half an ounce per pound of body weight, plus 12 ounces for each 30 minutes of exercise. A 160 lb person who exercises 30 minutes gets about 92 oz.
Is it 8 glasses a day?
Eight 8-ounce glasses is 64 oz, an easy target but only a rough one. Your weight, activity and weather can make your need higher or lower.
Do coffee, tea and food count?
Yes. All drinks count toward fluid intake, and food provides roughly 20% of the water most people take in.
What do health organizations suggest?
The U.S. National Academies suggest about 13 cups of fluid from drinks a day for men and about 9 cups for women, which is about 104 and 72 ounces.
How do I know if I am drinking enough?
Pale yellow urine and rarely feeling thirsty are common signs. Dark urine, headaches or dizziness can mean you need more fluid.
Can I drink too much water?
Yes, though it is uncommon. Very large amounts in a short time can lower sodium in the blood. Spread water through the day and follow your doctor’s advice if you have a condition.