Water Intake Calculator
Works out a daily water target in litres and 250 ml glasses from your body weight and minutes of exercise.
Recent
Formula
How the calculation works
The water target starts from body weight: each kilogram contributes 35 millilitres, so a 70 kg person begins with 2450 ml before any activity is counted.
Exercise minutes are then converted into 30-minute blocks, and every block adds 350 ml to cover the fluid lost through sweat during movement.
The total millilitres are divided by 1000 for litres and by 250 for glasses, giving two ways to see the same daily target.
Common mistakes
- Drinking the full target in one sitting overloads the body; spreading the litres across the day keeps hydration steady.
- Counting coffee, soft drinks or alcohol as plain water overstates hydration, since these can increase fluid loss instead.
- Ignoring hot weather, illness or breastfeeding keeps the target too low, because these conditions raise real fluid needs.
When to use it
- Use it on training days to see how much extra water your session adds before you fill a bottle for the gym.
- Use it when planning meals and desk time so the litres are spread into regular glasses rather than drunk in a rush.
Worked example
With a weight of 70 kg and 30 minutes of exercise, the base need is 2450 ml and the exercise adds 350 ml, giving 2800 ml. That is 2.8 litres or 11.2 glasses of 250 ml.
Common questions
Why does exercise add 350 ml for every 30 minutes?
Sweating during activity loses fluid, so the calculator adds a fixed 350 ml for each full or partial 30-minute block.
Are 250 ml glasses the only way to drink the target?
No. The glass figure is a convenience measure; any combination of bottles, cups or glasses that reaches the litre target works.
Related tools
-
Discount Calculator
See what you actually pay after a discount, and how much you save.
-
Tip Calculator
Add a tip to the bill and split it between people.
-
Add Tax / VAT Calculator
Add tax or VAT to a price to get the total.
-
Percentage Calculator
Find what percentage one number is of another.
-
Percentage Change
How much a number rose or fell between two points.
-
Monthly Budget Split
Divide monthly income into needs, wants and savings.
-
Profit Margin & Markup
Profit, margin and markup from a cost and a selling price.
-
Original Price from a Sale
Work back from a discounted price and the discount rate to the original.