A common rule of thumb sets daily water intake from body weight. This formula gives a baseline you can adjust for activity and climate.
Water (oz) = Weight (lb) × 0.5
What the terms mean
| Symbol | Meaning |
|---|---|
| Water | Daily water, in fluid ounces |
| Weight | Body weight, in pounds |
| 0.5 | Ounces per pound (use up to 0.67) |
Worked example
A 160 lb person needs about 160 × 0.5 = 80 oz, roughly ten 8 oz glasses a day.
Add for sweat and heat. Exercise, heat, and altitude all raise the requirement. Use the higher 0.67 factor on active or hot days, and let thirst guide the rest.
See the Hydration Calculator and the Water Intake Calculator.