Water Intake Calculator
How much water you need depends on your size, how much you sweat and how hot it is. This calculator uses a simple, widely quoted rule of thumb to give you a daily figure in ounces, liters and glasses.
Type a number and the answer appears straight away.
Water per day92 fl oz
- Liters
- 2.7
- US fluid ounces
- 92
- 8 oz glasses
- 11.5
- 500 mL bottles
- 5.4
A rule of thumb: half an ounce per pound of body weight, plus extra for exercise and heat. Food and other drinks count toward the total. General information, not medical advice.
The math behind it: Water Intake
water (fl oz) = body weight (lb) x 0.5 + 12 for every 30 minutes of exercise
Half an ounce per pound of body weight is the starting point, with about 12 fl oz (350 mL) added for each half hour of exercise and 10% more in hot or humid weather. A 160 lb person who exercises for 30 minutes comes out at 92 fl oz, or about 2.7 liters.
Water in food, tea, coffee and other drinks all counts toward the total. This is a rule of thumb, not medical advice: people with heart or kidney conditions may be told to drink less.
Common questions
How much water should I drink a day?
A common rule of thumb is half an ounce for each pound you weigh. At 160 lb that is 80 fl oz, about 2.4 liters or ten 8 oz glasses, before adding extra for exercise or heat.
Is 8 glasses of water a day enough?
Eight 8 oz glasses is 64 fl oz (1.9 liters), which suits a smaller, less active person. Larger people and anyone who exercises or lives somewhere hot will usually need more.
How do I know if I am drinking enough water?
The simplest check is the colour of your urine: pale yellow means you are well hydrated, and dark yellow means you need more. Thirst is a reliable guide for most healthy adults.
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