See how much water you should drink each day based on your body weight, exercise time, and climate — in ounces, liters, and cups.
How Much Water Should You Drink a Day?
The old 'eight glasses a day' rule is a rough guide, but your real needs scale with body weight, how much you sweat during exercise, and your climate. A common evidence-based starting point is about half an ounce of water per pound of body weight, adjusted up for activity and heat.
This calculator starts with roughly 0.5 ounces of water per pound of body weight (about 33 ml per kg). A 160 lb person begins around 80 oz, or about 2.4 liters. That baseline covers a typical day before accounting for exercise or hot weather.
Adjusting for Exercise and Climate
Hard exercise can cost you 16–32 oz of fluid per hour through sweat. This tool adds about 12 oz for every 30 minutes of activity. Hot, humid, or high-altitude conditions raise needs further, which is why the climate setting applies a multiplier on top.
Signs You're Drinking Enough
A practical gauge is urine color: pale straw means you're well hydrated, while dark yellow signals you need more. Thirst, headaches, and fatigue are later signs. Foods like fruit and vegetables also contribute to your daily fluid intake.
Tip: Spread water across the day rather than chugging large amounts at once. Keep a marked bottle nearby — the 'bottles per day' number above tells you exactly how many refills to aim for.
Frequently Asked Questions
How many ounces of water should I drink a day?
A common guideline is about half your body weight in ounces. A 160 lb person targets roughly 80 oz (about 2.4 liters) on a temperate day, more with exercise or heat. This calculator personalizes that figure.
Should I drink more water when I exercise?
Yes. Exercise increases fluid loss through sweat, often 16–32 oz per hour. Add roughly 12 oz of water for every 30 minutes of activity, and drink before, during, and after workouts to stay ahead of dehydration.
Can you drink too much water?
Yes, though it's rare. Drinking extreme amounts in a short time can dilute blood sodium (hyponatremia). Spread intake through the day and you'll be fine. The targets here are safe daily ranges for healthy adults.
Does coffee or tea count toward water intake?
Yes. Despite their mild diuretic effect, coffee and tea still contribute a net positive to your daily fluid intake. Water is best for the bulk of your needs, but caffeinated drinks do count.
How much water should I drink to lose weight?
Water itself doesn't burn fat, but drinking it before meals can reduce appetite and replaces high-calorie drinks. Meeting the target above supports metabolism and helps distinguish thirst from hunger.