Step-by-Step Calculation
- Take your body weight in pounds.
- Multiply by two-thirds (0.67) to get baseline ounces needed per day.
- Add roughly 12 ounces for every 30 minutes of exercise.
Worked Example
A 160 lb person who exercises for 45 minutes:
Baseline = 160 × 0.67 ≈ 107 oz
Exercise addition = 12 × 1.5 ≈ 18 oz
Total = 107 + 18 = 125 oz/day (about 15.6 cups, or roughly 3.7 liters) — nearly double the generic "8 glasses" (64 oz) recommendation for this active individual.
Frequently Asked Questions
Does coffee or tea count toward water intake?
Mostly yes — while caffeine has a mild diuretic effect, moderate caffeinated beverage consumption still contributes net positive hydration for most people.
Do I need more water in hot weather?
Significantly more — heat and humidity increase fluid loss through sweat well beyond this baseline formula, so add extra water on hot days or during intense outdoor activity.
