Pillar
Water Intake Calculator by Body Weight
Quick answer
To find your water intake by weight, drink about 0.5–0.75 oz per pound of body weight — roughly 30–40 ml per kg. A 150 lb (68 kg) adult needs about 75–113 oz (2.2–3.3 L) a day, before adding extra for exercise, heat, or pregnancy. Set your weight below for an exact number.
Fine-tune
Your daily goal
of water a day · about 11 glasses or 5.5 half-litre bottles
- 2.7
- Litres
- 91
- Ounces
- 11
- Glasses
Pace yourself
Spread it across the day and ease off after 9:00 PM for better sleep.
Electrolytes? Not needed
For everyday hydration, plain water and a normal diet cover your electrolytes just fine.
A friendly estimate for healthy adults, not medical advice. Your needs rise with heat, exercise, illness, pregnancy, and some medications. Don't drink more than ~1 litre per hour.
Daily water chart by weight
A quick reference in both pounds and kilograms. The low column is a mild, lightly active day; the high column reflects more activity or heat.
| Body weight | Low | High | Typical litres |
|---|---|---|---|
| 120 lb (54 kg) | 60 oz | 90 oz | 2.3 L |
| 140 lb (64 kg) | 70 oz | 105 oz | 2.6 L |
| 150 lb (68 kg) | 75 oz | 113 oz | 2.8 L |
| 160 lb (73 kg) | 80 oz | 120 oz | 3 L |
| 180 lb (82 kg) | 90 oz | 135 oz | 3.4 L |
| 200 lb (91 kg) | 100 oz | 150 oz | 3.7 L |
| 220 lb (100 kg) | 110 oz | 165 oz | 4.1 L |
| 250 lb (113 kg) | 125 oz | 188 oz | 4.6 L |
The simple formula
The most-used rule of thumb ties water to weight directly: about half an ounce of water for every pound you weigh, up to three-quarters of an ounce if you're active. In metric, that's roughly 30–40 ml per kilogram. It works because larger bodies have more cells, more blood volume, and a higher metabolic rate — all of which use water.
Weight is the starting point, not the whole story. Two people at 70 kg can have very different needs if one runs marathons in Arizona and the other works at a desk in Oslo. That's why the calculator layers activity and climate on top of the weight-based baseline. See the exact maths on the methodology page.
Frequently asked
How much water should I drink based on my weight?
Drink about half to three-quarters of an ounce of water per pound of body weight, which is roughly 30 to 40 ml per kilogram. A 150 lb (68 kg) person needs about 75–113 oz, or 2.2–3.3 litres, before adding extra for exercise and heat.
Is 'half your body weight in ounces' accurate?
It's a reasonable lower bound. Half your weight in ounces (0.5 oz/lb) covers a lightly active person in a mild climate. Active people, hot weather, and larger bodies push the figure up toward three-quarters of an ounce per pound or more.
How do I calculate water intake from kilograms?
Multiply your weight in kilograms by 30–35 ml for a baseline. A 70 kg adult is about 2.1–2.5 litres; add roughly 0.3–1.0 litre for activity and about 10% more in hot weather.
Sources
- 1.U.S. National Academies (IOM/NAM), 2005 — Adequate total water intake of about 3.7 L/day for men and 2.7 L/day for women, including water from food and all beverages.
- 2.European Food Safety Authority (EFSA), 2010 — Adequate total water intake of 2.5 L/day for men and 2.0 L/day for women under temperate conditions.
- 3.Mayo Clinic — General guidance of roughly 2.7–3.7 L of total fluids a day, with thirst and pale-yellow urine as everyday checks.