Water intake at 180 lb
A common starting point is 35 milliliters of water per kilogram of body weight, plus more for exercise. Here it is applied to 180 lb with 30 minutes of exercise.
How it works
Start with 35 milliliters for each kilogram you weigh. Add 350 milliliters for every 30 minutes you exercise. Divide milliliters by 29.5735 to get fluid ounces. For 180 lb with 30 minutes of exercise, the exercise part is 350 ml.
Worked example
Say a person weighs 180 lb with 30 minutes of exercise. That is 81.65 kg. The body weight part is 81.65 × 35 = 2857.75 ml. Exercise adds 350 × 30 divided by 30 = 350 ml. Together that is 3207.75 ml, which is 3.21 liters or 108.5 ounces. In cups that is 13.6.
Common questions
What if I exercise more or less than this?
Change the exercise minutes. Each 30 minutes adds 350 milliliters. At 30 minutes the page adds 350 ml. An extra 30 minutes would bring the total to 3557.75 ml.
Is 35 milliliters per kilogram right for everyone?
No. It is a common starting estimate. Heat, illness, pregnancy and some health conditions change needs. For 180 lb the starting figure is 2857.75 ml before exercise, and 3207.75 ml with 30 minutes of exercise.
Can I drink too much water?
Yes, though it is uncommon. Drinking far more than you need in a short time can dilute the salts in your blood. Spread your intake through the day. At 180 lb with 30 minutes of exercise, spread over 16 waking hours, 3.21 liters is about 200 ml an hour.
How many ounces or cups is that?
A US fluid ounce is 29.5735 milliliters and a cup is 8 ounces. At 180 lb with 30 minutes of exercise, 3207.75 ml is 108.5 ounces or 13.6 cups.
Do coffee and tea count toward my water?
Most drinks count toward your fluid total, though plain water is the simplest choice. At 180 lb with 30 minutes of exercise, 3.21 liters a day is about 14 cups spread across the day.