75 kg with 45 minutes of exercise in a hot climate
- Weight
- 75 kg
- Exercise a day
- 45 min
- Climate
- Hot
- Cups of coffee or tea
- 3
- Share of fluid from food
- 20%
Daily fluid3,675
35 x 75, plus 0.75 h x 600, plus 600, less a fifth from food
Open this exampleHealth & Fitnessnutrition
Water Intake Calculator
A daily fluid target from body weight, exercise and climate, separating total fluid from what actually needs drinking. Roughly a fifth of intake comes from food, and coffee and tea count toward the total rather than against it.
Also called: how much water should i drink, daily water intake.
Daily fluid
3,675
About 3,675 ml of total fluid a day, of which roughly 2,940 ml needs drinking. The climate adds 600 ml as a standing allowance, and raises the exercise cost to 600 ml an hour through higher sweat rates. Thirst and urine colour remain better daily guides than any formula. The 3 cups of coffee or tea count toward the total rather than against it. At normal intakes caffeine is not a net diuretic, so drinking extra water to offset coffee is unnecessary.
To drink
2,940
Base requirement
2,625
Added for exercise
450
Added for climate
600
Glasses of 250 ml
11.8
Litres to drink
2.94
On the climate
The climate adds 600 ml as a standing allowance, and raises the exercise cost to 600 ml an hour through higher sweat rates. Thirst and urine colour remain better daily guides than any formula.
On coffee and tea
The 3 cups of coffee or tea count toward the total rather than against it. At normal intakes caffeine is not a net diuretic, so drinking extra water to offset coffee is unnecessary.
Where the requirement comes from
| Source | Millilitres | Why |
|---|---|---|
| Body weight | 2,625 | About 35 ml a kilogram |
| Exercise | 450 | 600 ml an hour in this climate |
| Climate | 600 | Standing allowance for heat or cold |
| Less fluid from food | -735 | Roughly a fifth of intake comes from what you eat |
Method and background
This is what the calculation gives for the numbers you entered. It is an estimate, not advice, and it knows nothing about your situation beyond those numbers. Rules for United States change on a published schedule; the effective date is shown on every rule-based tool.
How this is calculated
The base requirement scales with body weight at around 35 ml a kilogram. Exercise adds roughly half a litre an hour, more in heat, and climate adds a standing allowance on top. Two corrections matter more than the arithmetic. Food supplies around a fifth of total fluid, so the amount to drink is less than the total requirement. And caffeinated drinks are not diuretic in net terms at normal intakes: a cup of coffee contributes more fluid than the caffeine causes to be lost, which makes the common advice to drink extra water to offset coffee simply wrong. Thirst and urine colour are better daily guides than any formula, and this page is a starting point rather than a prescription.
roughly 35 ml a kilogram, plus about 500 ml an hour of exercise, plus a climate allowance- w
- Weight in kilograms
- t
- Exercise minutes
Worked examples
Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
no exercise in a temperate climate
- Weight
- 75 kg
- Exercise a day
- 0 min
- Climate
- Temperate
- Cups of coffee or tea
- 0
- Share of fluid from food
- 20%
Daily fluid2,625
boundary: the base alone, which is where the eight glasses slogan comes from
Open this exampleMethod and limits
What it assumes
- A healthy adult with normal kidney and heart function.
What it deliberately does not model
- Heart failure and kidney disease often require fluid restriction, which reverses this advice entirely.
- Drinking far beyond thirst carries its own risk, since hyponatraemia comes from too much water and not too little.
Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator
Frequently asked questions
- Does coffee dehydrate me?
- Not in net terms at normal intakes. A cup contributes more fluid than the caffeine causes to be lost, so it counts toward the daily total rather than against it.
- Is eight glasses a day right?
- It is a slogan, not a finding. Requirements scale with body weight, activity and climate, and roughly a fifth of intake comes from food anyway.