How to calculate water intake
Water (oz) = weight (lb) × 0.5 + 12 × (exercise minutes ÷ 30)
Worked example. Drink about: 97 oz / day.
Example inputs — Body weight (lb): 170 lb; Exercise per day (minutes): 30 min. Starting values are illustrative.
Educational estimate — not medical advice.
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
A common rule of thumb is half an ounce of water per pound of body weight, plus about 12 oz for every 30 minutes of exercise. Food also provides some of your daily water. Needs rise in hot weather.
Assumptions & limitations
- Based on population formulas that may not fit athletes, pregnancy, children or medical conditions.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
Does coffee count?
Yes, most beverages contribute to hydration, including coffee and tea in moderate amounts.