How the goal is worked out
Base = body weight (lb) × 0.5 oz
+ 12 oz for every 30 minutes of exercise
+ 16 oz in hot or humid weather
This is a common rule of thumb. For comparison, the National Academies' general guide for total fluid from all sources is about 125 oz (3.7 L) a day for men and 91 oz (2.7 L) for women.
Worked example
A 160 lb person who exercises for 30 minutes a day gets 160 × 0.5 = 80 oz, plus 12 oz for exercise: 92 oz a day, about 2.7 liters or 11.5 cups.
Easy ways to drink more water
- Keep a refillable bottle with you and refill it at set times.
- Drink a glass with each meal and snack.
- Add lemon, cucumber or berries if you find plain water boring.
- Eat water-rich foods like watermelon, oranges, cucumber and soup.
- Drink a little extra before, during and after exercise.
Pair your water goal with a daily calorie target from the calorie calculator. This tool is for general information and is not medical advice.
Last reviewed October 2026.
Frequently asked questions
How much water should I drink a day?
The U.S. National Academies suggest a total daily fluid intake of about 3.7 liters (125 oz) for men and 2.7 liters (91 oz) for women, from all drinks and food. About 20% usually comes from food, so drinks make up the rest. Needs go up with heat and exercise.
What is the half-an-ounce-per-pound rule?
A popular rule of thumb is to drink about half an ounce of water for every pound of body weight, plus about 12 ounces for every 30 minutes of exercise. It is a simple starting point, not a scientific requirement.
Do coffee, tea and food count?
Yes. All drinks count towards your fluid intake, including coffee and tea, and so does water in food such as fruit, vegetables and soup.
How can I tell if I'm drinking enough?
Thirst and urine color are useful everyday signs. Pale yellow urine usually means you are well hydrated, while dark yellow suggests you need more fluid.
Can you drink too much water?
Yes, drinking very large amounts quickly can be harmful, especially during long endurance events. People with heart, kidney or other conditions may need to limit fluids, so they should follow their doctor's advice.