Rectangular tank capacity calculator
For underground and rooftop water tanks and basins: enter the inside dimensions and the current water level.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter length, width, height, water level and length unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Water volume = length × width × water level, capacity = length × width × height; 1 m³ = 1000 liters.
Example
Inputs: Length = 200, Width = 100, Height = 150, Water level = 120, Length unit = Centimeter (cm). Result: Liquid volume: 2,400 L; Total tank capacity: 3,000 L; Fill percentage: 80%.
Limits and caveats
- Assumes vertical walls and a level floor; use inside dimensions, not outside.
- Does not subtract floats or pipes inside the tank.
Questions about this tool
How many liters in a 2 × 1 × 1.5 m tank?
It holds 3 m³, exactly 3000 liters.
I entered centimeters. How do I get liters?
The calculator converts for you; every 1000 cm³ is one liter.
Should I use the outside size of a concrete tank?
No. Subtract the wall thickness from each dimension, or the capacity will read too high.