Volume Calculator
Work out the volume of any rectangular space or container — rainwater tanks, planter boxes, excavation pits, fish ponds or skip bins — in cubic metres and litres.
Enter your measurements
Your m³ of volume result will appear here instantly.
How to use this calculator
- 1
Measure the internal length, width and depth of the space or container.
- 2
Use the same unit for all three measurements.
- 3
For containers, measure to the water line or fill level, not the brim.
- 4
Remember 1 m³ = 1,000 litres when comparing against tank or bag sizes.
How the calculation works
Volume
Volume = length × width × depth. A 2 × 1.5 × 1 m tank holds 3 m³ = 3,000 litres. Litres are simply cubic metres × 1,000.
Worked example
A garden pond 2.5 m × 1.5 m, dug to 0.6 m deep.
Volume = 2.5 × 1.5 × 0.6 = 2.25 m³ = 2,250 litres.
The pond holds approximately 2,250 litres — remember to allow for liner overlap, pump displacement and rocks if stocking fish.
Frequently asked questions
How many litres are in a cubic metre?
Exactly 1,000. That's the whole metric system working for you: a 10,000 L rainwater tank holds 10 m³, and a 50 L bag of soil is 0.05 m³.
Can I calculate cylinder volumes (round tanks, post holes)?
This calculator handles rectangles only. For a cylinder, the volume is π × radius² × depth — a 300 mm post hole 600 mm deep holds about 0.042 m³. A dedicated footings calculator is on the roadmap.
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Results are estimates only. Always confirm material requirements with your supplier or a qualified professional before purchasing.