Nominal geometric size can exceed working capacity because tanks need freeboard and may contain internal fittings.
How to calculate tank volume
Choose the shape
Select the option that most closely matches the usable inside of your tank.
Enter dimensions
Select one measurement unit and enter positive internal dimensions.
Read and convert
Choose the primary result unit, then compare the automatic conversions.
Tank Size in Litres formula
The calculator first finds geometric volume, then applies 1 cubic metre = 1,000 litres.
RectangularV = length × width × heightCylinderV = π × radius² × height or lengthCone bottomV = cylinder volume + (π × radius² × cone height) ÷ 3Common tank volume conversions
| Starting volume | Equivalent |
|---|---|
| 1 cubic metre (m³) | 1,000 litres |
| 1 litre | 0.264172 US gallons |
| 1 US gallon | 3.785411784 litres |
| 1 Imperial gallon | 4.54609 litres |
| 1 cubic foot | 28.316846592 litres |
| 1 US oil barrel | 42 US gallons / 158.987 litres |
Common uses
Frequently asked questions
How does this tank size in litres calculator work?
The calculator first finds geometric volume, then applies 1 cubic metre = 1,000 litres. It normalizes every measurement to metres, calculates the selected geometry, and converts that result to the output unit you choose.
Should I enter internal or external tank dimensions?
Use internal dimensions when estimating liquid capacity. External dimensions include the tank wall, insulation, or cladding and normally produce an overestimate.
What is the difference between total and filled volume?
Total capacity is the geometric volume at 100%. Filled volume applies the percentage control, which is useful for freeboard or an operating level below the top.
How accurate is the result?
The geometry and unit conversions use precise constants, but the practical result depends on measurement accuracy, tank shape, wall thickness, fittings, and internal displacement.