Formula
Measured volume = length × width × height. Litres = cubic metres × 1,000. Cubic feet = cubic metres × 35.3146667215. Optional planning volume = measured volume × (1 + allowance percent ÷ 100).
Volume Calculator
Calculate the volume of a rectangular box, room, container or prism from length, width and height, with litres, cubic metres and cubic feet shown for checking.
What-if check
Three dimensions kept visible
Volume is length times width times height; the proof table keeps all three source dimensions beside the cubic result.
| Check | Value | Note |
|---|---|---|
| length | 2.4 m | first dimension |
| width | 1.8 m | second dimension |
| height/depth | 0.6 m | third dimension |
| litres | 2,592 L | 1 m3 = 1,000 L |
| current output | 2.592 m³ | rectangular prism volume |
Visual proof
Result path
2.4 m × 1.8 m × 0.6 m = 2.592 m³. That is 2,592 L or 91.54 ft³; planning volume with 0% allowance is 2.592 m³.
Worked example
For a box or space 2.4 m long, 1.8 m wide and 0.6 m high: 2.4 × 1.8 × 0.6 = 2.592 m³. Litres are 2.592 × 1,000 = 2,592 L. Cubic feet are 2.592 × 35.3146667215 = about 91.54 ft³.
Professional note
Master’s Tip: write the three source dimensions beside the result. Most volume mistakes come from mixing centimetres, millimetres, feet and metres, or from hiding an ordering allowance inside the geometric volume.
Regional and unit assumptions
The default basis uses SI metres and cubic metres. Litres are shown because 1 m³ equals 1,000 L. Cubic feet are shown with the international-foot relationship for imperial cross-checks.
Assumptions and limitations
- The main calculation assumes a rectangular prism: straight length, width and height/depth.
- Default inputs are metres, so the main result is cubic metres. Convert inches, feet or centimetres first if your measurements are in mixed units.
- The optional allowance is separated from measured volume so quote notes and classroom work can show what is geometry and what is judgement.
- Irregular shapes, sloped bottoms, rounded tanks, settlement, compaction and supplier rounding need their own method or professional check.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Measured volume = length × width × height. Litres = cubic metres × 1,000. Cubic feet = cubic metres × 35.3146667215. Optional planning volume = measured volume × (1 + allowance percent ÷ 100).
Standard or basis
The default basis uses SI metres and cubic metres. Litres are shown because 1 m³ equals 1,000 L. Cubic feet are shown with the international-foot relationship for imperial cross-checks.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: write the three source dimensions beside the result. Most volume mistakes come from mixing centimetres, millimetres, feet and metres, or from hiding an ordering allowance inside the geometric volume.
Related calculators
Questions
How do you calculate volume?
For a rectangular prism, multiply length by width by height. The result is in cubic units, such as cubic metres, cubic feet or cubic centimetres.
What is the formula for box volume?
Box volume is length × width × height. Keep all three dimensions in the same unit before multiplying.
How many litres are in a cubic metre?
One cubic metre equals 1,000 litres, so multiply cubic metres by 1,000 to get litres.
Can I use this for concrete, gravel or mulch?
Yes for a simple rectangular volume check, but dedicated material calculators are better when depth units, waste, density, bag size or supplier rounding matter.
Does the allowance change the true volume?
No. The measured geometric volume stays the same. The allowance is a planning layer for ordering margin, tolerance, spillage or voids.
Calculation note
Volume is the three-dimensional partner of area. A rectangle’s area measures a surface; a rectangular prism’s volume measures the space filling that surface through a height or depth. Keeping cubic units visible helps prevent the common mistake of treating length, area and volume as interchangeable.
Volume is area carried through depth
A rectangular-prism volume can be read as base area multiplied by height. First length × width gives a flat area; multiplying by height turns that area into a stack of equal layers. This is why a shallow tray, a storage box and a concrete footing can all use the same core formula when their sides are straight.
Cubic units are not square units
The unit changes when the third dimension enters the calculation. Metres × metres gives square metres; metres × metres × metres gives cubic metres. A printed volume record should therefore preserve all three original dimensions, not only the final cubic answer.
Litres make cubic metres easier to use
For water, tanks and containers, litres are often easier to picture than cubic metres. The SI relationship is simple: 1 cubic metre equals 1,000 litres. The calculator shows both so a classroom worksheet, quote note or container record can be read in the unit the reader expects.
Allowances are practical decisions, not geometry
Ordering extra material can be sensible, but it should not be confused with the measured shape. The page keeps measured volume and planning allowance separate so a supplier, teacher, homeowner or tradie can see where the arithmetic ends and judgement begins.
Sources and further readingNIST: SI UnitsNIST Special Publication 811: Guide for the Use of the International System of Units