Quick Answer — How Much Water Should You Drink Daily?
The most widely used starting point is half your body weight in pounds, taken as fluid ounces of water.
The baseline formula: Baseline beverages (oz) = Body weight (lb) × 0.5
That is the same thing as roughly 32.6 ml per kilogram of body weight, so the imperial and metric rules of thumb agree with each other.
Quick reference (baseline, sedentary, temperate climate):
- 150 lb → 75 oz = 2.22 L = 9.4 cups
- 160 lb → 80 oz = 2.37 L = 10.0 cups
- 180 lb → 90 oz = 2.66 L = 11.3 cups
- 200 lb → 100 oz = 2.96 L = 12.5 cups
- 220 lb → 110 oz = 3.25 L = 13.8 cups
Then adjust it. This calculator scales the baseline by climate, adds 12 oz for every 30 minutes of moderate exercise, and adds a fixed allowance for altitude, pregnancy or breastfeeding.
Worked example: a 160 lb person doing 45 minutes of moderate exercise in a temperate climate needs 80 × 1.00 + 45 × 0.4 = 98 oz of beverages per day — about 2.90 L, or 12.25 cups (the calculator rounds this to 12.3).
One caveat that most calculators skip: the half-your-weight rule is a *beverage* target. Food supplies roughly another 20% of your total water, so that same person is taking in about 122.5 oz (3.62 L) of total water once meals are counted.