Suggested fluid intake is often used interchangeably with suggested water intake, but fluid requirements are met through both foods and drinks. In fact, food typically provides roughly 20% of your fluid needs.

There are many methods for calculating daily fluid requirements. One simple equation for adults is 0.5 fluid ounces per pound of body weight per day.

0.5 fl oz x Body Weight in lbs. = Daily Fluid Requirement in fl oz ^†

Example

If you weigh 150 pounds, multiply 150 by 0.5 to estimate your daily fluid needs.
150 lbs x 0.5 = 75 fl oz of fluid

If you assume that food provides 20% of your fluid needs, you can multiply your daily fluid requirement by 0.8 to get an estimate of how much water you need to drink per day.

Example

75 fl oz x 0.8 = 60 fl oz of water

As you calculate your daily fluid requirements, you will likely find that the number is close to the common recommendation of 64 - 96 fl oz per day. Keep in mind that fluid requirements increase under extreme conditions such as exercise in hot and humid weather and during illness.

^† If you are significantly overweight, this equation may overestimate your fluid needs.

Additional Resources

• Mayo Clinic: Water: How much should you drink every day?

Lori Rice, M.S., is a nutritional scientist and author with a passion for healthy cooking, exercise physiology, and food photography.