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Result
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Formula
Daily water (liters) = weight (kg) × 0.033
Example
70 kg person should aim for about 2.3 liters/day as a general estimate.
How does this water intake formula work?
Start with weight × 0.033 litres. Then scale it: Light stays the same, Moderate adds 20%, and High adds 40%. The page rounds the display to two decimal places.
The 0.033 figure is a simple teaching rule of thumb, about 33 millilitres per kilogram. It is not a medical requirement and it ignores climate, diet, and health conditions.
Fluid also comes from food. The number on this page is not an instruction to drink that many litres of plain water on top of everything else.
Who should not use this estimate as a target?
People with kidney, heart, or fluid-balance conditions, and anyone who has been told to limit or increase fluids, should follow that personal advice instead of this formula.
Thirst, urine colour, heat, and illness can matter more than a weight formula. This page is for learning the arithmetic, not for treatment.
How to use this calculator
- Enter weight in kilograms. The 0.033 factor is applied to kilograms. Pounds will not match the formula.
- Choose an activity level. Light uses 1, Moderate uses 1.2, and High uses 1.4.
- Read litres per day. The result is a general estimate. It is not a prescription for illness, heat, sport, or pregnancy.
Questions about Water Intake Calculator
Why is the 70 kg example about 2.3 litres while Moderate gives more?
About 2.3 litres is 70 × 0.033, the base. Choosing Moderate multiplies that base by 1.2, so the result is higher.
Does tea, milk, or food count?
The calculator does not subtract other fluids. It only runs weight and the activity multiplier.
Is more always better?
No. The page does not set a maximum, and drinking far beyond what you need can be harmful. Use the result as a rough learning figure.
Can I enter weight in pounds?
Not directly. Convert pounds to kilograms first. The unit converter can do that pair.
Read the guide
Daily water on this page starts at body weight in kilograms times 0.033 litres. Light activity keeps that base. Moderate multiplies by 1.2. High multiplies by 1.4. A 70 kg person at the base is about 2.31 litres. The same person at Moderate is about 2.77 litres. This is not a medical target.
Open “What the water-intake estimate is actually doing”What this helps you do
- Estimate Water Intake from the inputs you already have.
- Check the result against the formula and the worked example.
- Change one value at a time and compare the new estimate.
Limits to keep in mind
- The figure is only as complete as the inputs on this form.
- Rounding, fees, and local rules can change the real-world number.
- Use it to learn and compare. Confirm important finance or health decisions with a qualified professional.