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Water Intake Calculator
Get a daily water target from your body weight and how long you exercise. The calculator uses the common rule of half your body weight in pounds as fluid ounces, then adds an allowance for each half hour of activity.
- 8 oz glasses
- 11.5
- From body weight
- 80 fl oz
- Added for exercise
- 12 fl oz
Saved setups
Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.
Your recent calculations
Results you calculate here are kept on this device so you can come back to them.
Formula
How to use it
- Enter your body weight in pounds or kilograms.
- Enter the minutes of exercise you do on a typical day.
- Read your target in fluid ounces, liters or cups, and as a count of 8 oz glasses.
Worked examples
A 160 lb adult who exercises 30 minutes a day (80 + 12 = 92 fl oz)
- Daily water target
- 92 fl oz
- From body weight
- 80 fl oz
- 8 oz glasses
- 11.5
A 70 kg adult on a rest day (about 77 fl oz)
- Daily water target
- 77.2 fl oz
- 8 oz glasses
- 9.6
How to use the number
There is no single scientifically fixed water requirement; this is a rule of thumb. For reference, the US National Academies set an adequate intake of total water — from all drinks and food — of about 3.7 liters a day for men and 2.7 liters for women. Around a fifth of that typically comes from food.
Needs rise in hot weather, at altitude, during pregnancy and breastfeeding, and with illness. Tea, coffee, milk and other drinks count toward the total. Pale yellow urine and rarely feeling thirsty are practical signs you are drinking enough.
People with heart or kidney conditions are sometimes told to limit fluids. This is an estimate for general information, not medical advice. Talk to a doctor or other qualified clinician before making health decisions based on it.
Questions people ask
How much water should I drink a day?
By the half-your-weight rule, a 160 lb adult would aim for about 80 fl oz (2.4 liters) a day, or 92 fl oz with 30 minutes of exercise — about eleven and a half 8 oz glasses.
Is eight glasses a day enough?
Eight 8 oz glasses is 64 fl oz (1.9 liters). That is a reasonable floor for many adults, though larger or more active people will usually want more.
Does coffee count toward water intake?
Yes. Caffeinated drinks have a mild diuretic effect but still add more fluid than they cause you to lose.