Water Intake Calculator
Find out how much water you should drink each day based on your body weight, physical activity level, and climate. Staying properly hydrated supports energy levels, digestion, skin health, and overall well-being.
Daily Water
2.8liters
Glasses per Day
11glasses
Cups per Day
11cups
Your daily glasses at a glance
of 5 L max scale
How to use
Enter your body weight in kilograms, select your typical activity level, and choose the climate you live in. The calculator computes your recommended daily water intake in liters and translates it into standard 250ml glasses for easy tracking throughout the day.
Method
The base recommendation is approximately 33ml per kilogram of body weight. This is adjusted upward for higher activity levels (add 0.5-1L for moderate to intense exercise) and warmer climates (add 0.5-1L for hot or humid conditions). Individual needs may vary based on health conditions, diet, and other factors. Consult a healthcare professional for personalized advice.
When this calculator helps
Proper hydration impacts energy levels, cognitive function, digestion, skin health, and athletic performance, yet most people do not drink enough water. This calculator personalizes your daily target based on your actual body weight, activity level, and climate rather than relying on generic one-size-fits-all advice. Athletes, outdoor workers, people in hot climates, and anyone trying to build better hydration habits will benefit from having a specific daily goal in liters and glasses they can track throughout the day.
Examples
Example 1: Office Worker in Temperate Climate
A 70 kg (154 lb) person with a sedentary desk job in a mild climate has a base intake of 2.3 liters per day, which equals about 9 glasses of 250ml. This person should aim to drink one glass every hour during an 8-hour workday plus one more in the morning and evening.
Example 2: Active Runner in Hot Weather
An 85 kg (187 lb) runner training in a hot climate needs a base of 2.8 liters, plus up to 1 liter for high activity and 1 liter for heat, totaling roughly 4.8 liters (about 19 glasses) per day. On rest days, they can reduce to about 3.3 liters.
Example 3: Lightweight Person with Moderate Activity
A 55 kg (121 lb) person who does yoga three times a week in a cool climate has a base of 1.8 liters plus about 0.5 liters for moderate activity, totaling around 2.3 liters or 9 glasses. Keeping a reusable bottle at their desk helps them hit this target naturally.
Things to watch
- •Start your day with a glass of water, after 7-8 hours of sleep, your body is naturally dehydrated and needs to rehydrate.
- •Fruits and vegetables (watermelon, cucumber, oranges) contribute to hydration, about 20% of daily water intake comes from food.
- •Set phone reminders or use a marked water bottle to spread intake evenly throughout the day rather than drinking large amounts at once.
- •Drinking too much water too quickly can cause hyponatremia (low sodium levels), spread your intake over the full day.
- •If you feel hungry between meals, try drinking water first, thirst is often mistaken for hunger by the body.
Sources and methodology
Last reviewed: April 25, 2026. We review formulas, default assumptions, and examples against public references when a formal source applies.
Method: This calculator uses the formula explained on this page, then checks default assumptions and examples against the references listed below.
- •Dietary Guidelines for Americans, 2020-2025, U.S. Department of Health and Human Services
- •Water, Hydration, and Health, National Institutes of Health
Found something off? Send a correction with the page URL, inputs, result, and expected result.
Common questions
- How much water should I drink per day?
- A general guideline is about 0.5-1 ounce per pound of body weight. A 160-pound person should aim for 80-160 ounces (2.4-4.7 liters). Activity level, climate, and diet affect your needs, you need more if you exercise heavily or live in hot weather.
- Is the '8 glasses a day' rule accurate?
- The 8×8 rule (eight 8-ounce glasses) is a reasonable starting point at 64 ounces, but it's not based on strong science. Your actual needs depend on your body size, activity level, and climate. Most people can trust their thirst as a guide.
- Can I count coffee and tea toward my water intake?
- Yes, coffee and tea do contribute to your daily hydration despite being mild diuretics. Studies show the fluid gained far outweighs the small diuretic effect. However, heavily caffeinated energy drinks and alcohol have stronger dehydrating effects and should not be counted as equivalent hydration sources.
- What are the signs of dehydration?
- Early signs include dark yellow urine, thirst, dry mouth, fatigue, and headaches. More serious dehydration causes dizziness, rapid heartbeat, and confusion. A simple check: if your urine is pale yellow or clear, you are likely well hydrated. Dark amber urine suggests you need to drink more water.
- Should I drink more water when exercising?
- Yes. The American College of Sports Medicine recommends drinking 16-20 ounces of water 2 hours before exercise, 7-10 ounces every 10-20 minutes during exercise, and another 16-24 ounces for every pound of body weight lost through sweat. For workouts over an hour, consider a sports drink with electrolytes.