Water Intake Calculator
Daily fluid recommendation, adjusted for body weight, activity, and climate.
Daily target
Recommended fluid (beverages)
0
liters / day
In ounces
0
In 8-oz cups
0
Weight-based
0
IOM beverages
0
Where the numbers come from
Two methods are averaged:
- Weight-based — the popular rule of thumb: half your body weight in ounces. Easy to remember, not from any single authoritative source.
- IOM beverages-only — the Institute of Medicine's total daily fluid guidelines (3.7L men / 2.7L women) times 0.8 to remove the ~20% that comes from food.
Both get bumped up for activity (+0.35 to +1.2 L for light to intense) and hot climate (+0.5 L).
You probably don't need to track this
Your thirst is reliable. Pale-yellow urine = adequately hydrated. Use this as a sanity check, not a daily target to obsess over. Drink when you're thirsty, slightly more when it's hot or you've worked out.