Water Intake Calculator
Enter your weight, how much you exercise and whether the weather is hot to see a general estimate of daily fluid intake in liters and ounces.
Last updated November 2, 2026
Result
About 2.6 liters (88 oz) of fluids a day
| Measure | Value |
|---|---|
| Body weight | 150 lb |
| Daily fluids | 2.6 L |
| In US fluid ounces | 88 oz |
| In 8 oz glasses | 11 |
Rule of thumb: 33 ml per kg of body weight, plus 350 ml for every 30 minutes of exercise, plus 10% in hot weather. Fluids include water, other drinks and the water in food. Needs vary, and people with heart, kidney or other conditions may be told to limit fluids. General estimate only, not medical advice. Talk to a qualified health professional about your own situation.
Show the work
Formula: Fluids (ml) = 33 × weight (kg) + 350 × (exercise minutes ÷ 30), plus 10% in hot weather.
- You entered 150 lb (68 kg), 30 minutes of exercise, mild or cool weather.
- Body weight: 33 × 68 = 2,245 ml.
- Exercise: 350 × (30 ÷ 30) = 350 ml.
- Total: 2,245 ml + 350 ml = 2,595 ml.
- Convert: 2,595 ml = 2.6 L, and ÷ 29.5735 ml per US fluid ounce = 88 oz (11 glasses of 8 oz).
Result: About 2.6 liters (88 oz) of fluids a day
How the fluid estimate is calculated
fluids (ml) = 33 × weight (kg) + 350 × (exercise minutes ÷ 30), then × 1.1 if hot
The estimate starts with 33 ml of fluid per kilogram of body weight, adds 350 ml for each 30 minutes of exercise, and adds 10% in hot or humid weather. For a 150 lb (68.0 kg) person exercising 30 minutes: 68.04 × 33 + 350 = 2,595 ml, about 2.6 liters or 88 US fluid ounces.
The result counts all fluids, including water, other drinks and the water in food, not only plain water. The US National Academies has set general total-water intake levels of about 2.7 liters a day for women and 3.7 liters for men, which includes water from food. Your thirst, urine color and a doctor’s advice are better guides than any formula.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: BMI Calculator, Protein Calculator and Ideal Weight Calculator.
This is an estimate, not medical advice
This is a rule-of-thumb estimate for healthy adults, not a medical standard. Fluid needs vary with health, medicines, pregnancy and breastfeeding, and some conditions require limiting fluids. Ask a health professional about your own needs. This page has not been reviewed by a medical professional.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (news release of February 11, 2004). Context only: sets adequate total water intake at about 3.7 liters a day for men and 2.7 liters for women, counting water from beverages and food, for healthy sedentary people in temperate climates
The formula on this page (33 ml per kg, plus 350 ml per 30 minutes of exercise, plus 10% in hot weather) is a rule of thumb. We did not find a published source for it, and the National Academies figures above are not derived from it.
How to use the Water Intake Calculator
- Choose units and enter your weight.
- Enter your daily exercise time and pick the weather.
- Read the estimate in liters, ounces and glasses, then use Copy, Print or Share.
Worked example
A 150 lb person (68.0 kg) who exercises 30 minutes a day in mild weather: 68.04 × 33 + 350 = 2,595 ml, about 2.6 L or 88 oz. In hot weather add 10%, about 2.9 L.
| Weight | Liters per day | US fluid ounces |
|---|---|---|
| 120 lb (54 kg) | 2.1 | 73 |
| 150 lb (68 kg) | 2.6 | 88 |
| 180 lb (82 kg) | 3.0 | 103 |
| 210 lb (95 kg) | 3.5 | 118 |
Frequently asked questions
How much water should I drink a day?
It depends on your body, activity, weather and health. This tool gives a rough estimate of total fluids, not only water.
Do coffee, tea and food count?
Yes. Most drinks and the water in food count toward total fluid intake.
Can I drink too much water?
Yes, though it is uncommon. Drinking far more than you need can be harmful, so do not force fluids beyond thirst without medical advice.
Does this apply in pregnancy or illness?
Needs can change, so ask your doctor.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser and nothing you enter is saved or uploaded.