Water Intake Calculator
How much water to actually drink daily, based on your weight and activity.
Recommended daily water intake
97 oz
Cups
12.1
Liters
2.9
Worked example
A 170 lb person who exercises 45 minutes a day: baseline 170 ÷ 2 = 85 oz, plus 45 ÷ 30 × 12 = 18 oz for the workout, for 103 oz a day -- that is 12.9 cups or 3.0 litres, roughly 6.1 standard 500 ml bottles.
Daily water by bodyweight and exercise
| Weight | 0 min/day | 30 min/day | 60 min/day | 90 min/day |
|---|---|---|---|---|
| 120 lb | 60 oz (1.8 L) | 72 oz (2.1 L) | 84 oz (2.5 L) | 96 oz (2.8 L) |
| 140 lb | 70 oz (2.1 L) | 82 oz (2.4 L) | 94 oz (2.8 L) | 106 oz (3.1 L) |
| 160 lb | 80 oz (2.4 L) | 92 oz (2.7 L) | 104 oz (3.1 L) | 116 oz (3.4 L) |
| 180 lb | 90 oz (2.7 L) | 102 oz (3.0 L) | 114 oz (3.4 L) | 126 oz (3.7 L) |
| 200 lb | 100 oz (3.0 L) | 112 oz (3.3 L) | 124 oz (3.7 L) | 136 oz (4.0 L) |
| 220 lb | 110 oz (3.3 L) | 122 oz (3.6 L) | 134 oz (4.0 L) | 146 oz (4.3 L) |
| 240 lb | 120 oz (3.5 L) | 132 oz (3.9 L) | 144 oz (4.3 L) | 156 oz (4.6 L) |
When the estimate needs adjusting
- Heat and humidity. Sweat losses on a hot day can exceed what the exercise term covers. Add 8-16 oz on days you are outdoors in heat, more if you sweat visibly at rest.
- Altitude, flights, dry indoor air. All three increase losses through breathing; a long flight can take a litre without you noticing.
- Food counts. Fruit, vegetables, soups, and coffee all hydrate. The target here is drinking water, so a day heavy in those needs less from the glass.
- The simplest check is colour. Pale straw urine means you are there. Clear all day means you can ease off; dark yellow means catch up.
- More is not better. Drinking far beyond thirst during long endurance events can dilute blood sodium. Athletes going over three hours should drink to thirst and take electrolytes, not chase a number.
Keep going
- Hydration and food targets both move with your bodyweight and activity; the macro calculator covers the food side of the same daily plan. Macro Calculator
Frequently Asked Questions
Where does the "half your bodyweight in ounces" rule come from?
It's a widely-published, commonly-cited baseline for daily water intake, not a single settled clinical formula -- actual needs vary by climate, individual physiology, and how much water-rich food you eat. Treat it as a solid starting point, not an exact medical requirement.
Why does exercise add to the total?
You lose real water through sweat during exercise, on top of your baseline needs. This adds 12oz for every 30 minutes of activity, a standard addition used by most mainstream hydration guidance.
Does this count water from food and other drinks?
No -- this is a target for water intake specifically. Food and other beverages do contribute real hydration too, so this number is a reasonable target to aim for through drinking water, not the only fluid you're allowed.
Does coffee or tea count toward the total?
Yes. Caffeine is a mild diuretic, but the water in a cup of coffee more than covers it; studies comparing coffee to water find no meaningful difference in hydration for regular drinkers. Alcohol is the exception -- it dehydrates on net.
Can I drink too much water?
Yes, though it takes effort. The risk is hyponatraemia -- blood sodium diluted by drinking far beyond what the kidneys can clear (roughly a litre an hour) -- seen mainly in endurance events and rare compulsive drinking. For everyday life, drinking to the target plus thirst is safe; forcing a gallon on a sedentary day is not better than this number, just more bathroom trips.