Use inside dimensions for liquid capacity. Outside measurements can overstate volume because of wall thickness and insulation.
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.
Volume in Litres formula
Each shape is solved in cubic metres, then multiplied by 1,000 for 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 volume in litres calculator work?
Each shape is solved in cubic metres, then multiplied by 1,000 for 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.