# Daily Water Intake Calculator

> Free daily water intake calculator. Enter your weight, activity level, and climate to get a personalized hydration target in liters, glasses, and bottles.

Eight glasses a day is a guess. Your weight, how much you move, and how hot it is change the real number. Enter the three and get a daily water target in liters, glasses, and bottles.

*Interactive tool: enter your values at https://toollantern.win/water-intake-calculator/ and results update instantly in your browser.*

## The formula

There is no single official number, but sports-medicine guidelines converge on a simple starting point: about **35 ml of water per kilogram of body weight** per day for a sedentary adult in a temperate climate. This calculator starts there and adds for sweat loss: +350 ml for light activity (a walk or light chores), +700 ml for moderate exercise (a real workout), +1000 ml for intense training or a physical job, and +500 ml in hot or humid weather.

## Worked example

A **70 kg** person with **moderate** activity in a **hot** climate: base = 70 x 35 = 2450 ml, plus 700 ml for activity, plus 500 ml for heat = **3.65 liters** per day, about **15 glasses** of 250 ml. Roughly 20% of that usually comes from food (fruit, vegetables, soups), so the drinking target lands near 2.9 liters.

## What to do with the number

Use the target as a daily baseline, then adjust by thirst, urine color (pale straw is the goal), and how you feel during workouts. Hydration needs rise with training load, so pair this with the [TDEE calculator](/tdee-calculator/) to match your fueling to your activity, and the [running pace calculator](/running-pace-calculator/) if you are training for a race and need a drink plan for long runs.

## Frequently asked questions
### Is the 8-glasses-a-day rule right for everyone?

No. Eight glasses (about 2 liters) is a reasonable floor for a smaller sedentary adult, but a larger or active person often needs 3 liters or more. Weight, activity, and heat change the answer a lot.

### Does coffee count toward my water intake?

Mostly yes. Coffee and tea hydrate you almost as well as water; the mild diuretic effect does not cancel out the fluid. They still count toward your daily total.

### Can you drink too much water?

Yes, but it is rare and usually involves extreme overdrinking during endurance events. For normal daily life, spreading your target across the day keeps you well clear of any risk.

### Does water from food count?

About 20% of daily water typically comes from food, especially fruit, vegetables, and soups. The calculator's total includes that, so your drinking target is a bit lower than the headline number.

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Interactive version: https://toollantern.win/water-intake-calculator/