What is the Water Tank Capacity Calculator?
Find the capacity of a rectangular or round water tank in litres and gallons.
Enter tank shape, length or diameter, width (rectangular only) and height and the Water Tank Capacity Calculator returns capacity, in UK gallons and volume. Results update as you type, and nothing you enter leaves your device.
How it is calculated
Rectangular: volume = length × width × height
Round: volume = π × (diameter ÷ 2)² × height
1 cubic foot = 28.317 litres
How to use it
- Choose tank shape.
- Enter length or diameter in ft.
- Enter width (rectangular only) in ft.
- Enter height in ft.
- Read capacity in the results panel. It updates as you type.
- Change any value to compare scenarios, or use Share to send the result as a link.
Worked example
Common questions
What formula does the Water Tank Capacity Calculator use?
It uses: Rectangular: volume = length × width × height; Round: volume = π × (diameter ÷ 2)² × height; 1 cubic foot = 28.317 litres.
What do I need to use the Water Tank Capacity Calculator?
You need tank shape, length or diameter, width (rectangular only) and height. Sensible starting values are filled in so you can see how it works straight away.
Is the Water Tank Capacity Calculator free, and is my data stored?
It is free with no sign-up. The calculation runs in your browser, so the values you enter are not sent to or stored on our server.