Room volume calculator: cubic metres.
Enter your own measurements in metres to calculate a rectangular room envelope in cubic metres. This free calculator runs in the page without an account. It does not extract dimensions from a scan or image.
The calculation: width × depth × height.
For a rectangular prism, multiply the three perpendicular dimensions in the same unit. A room envelope measuring 3 m × 4 m × 2.5 m has a geometric volume of 30 m³. Doubling height while keeping the floor dimensions unchanged doubles that envelope volume. This is a calculation from the numbers you provide, not a verification of those measurements.
Use metres consistently.
Measure the boundaries you want to describe and record them on a sketch. Convert centimetres to metres before entering them: 250 cm becomes 2.5 m. You may use a decimal point or comma, with no thousands separators. Each dimension must be greater than zero and no more than 1000 m. The result uses up to ten significant digits for readability; extra displayed digits do not establish measurement accuracy.
Check whether a rectangular envelope fits.
This model assumes straight perpendicular walls, a level floor and a flat ceiling at one height. For a sloping ceiling, alcove, curved wall or split level, one width, depth and height cannot describe the full geometry. Record those exceptions and choose a calculation method that models the separate shapes. Do not invent an average height or silently use the highest point as though the result described the actual interior.
Envelope volume is not usable air or HVAC capacity.
Furniture, built-ins and other obstructions are not subtracted here. Open connections to adjacent rooms are not modeled. The result therefore does not establish usable air volume, ventilation requirements or heating and cooling capacity. Use an appropriate assessment with its required inputs for those decisions; this geometric result alone is insufficient.
Keep the inputs with the result.
Copy the selectable result into your own notes and add the room name, measurement date, source and boundary assumptions. Check important dimensions on site. Editing any input clears the previous answer so it cannot be mistaken for a new calculation. Reset restores the 3 × 4 × 2.5 m example and clears the output.
About this calculation.
How do I calculate room volume in cubic metres?+
For a rectangular room envelope, multiply width by depth by height, all in metres. For example, 3 × 4 × 2.5 = 30 m³.
Can I enter centimetres or feet directly?+
No. Convert each measurement to metres first. For example, 250 centimetres is 2.5 metres. The fields accept a decimal point or comma but no unit text.
Does this calculate usable air volume or heating capacity?+
No. It calculates only a rectangular geometric envelope. Obstructions, adjacent spaces and the other inputs needed for ventilation or heating design are not assessed.
Can I use this for a sloping ceiling?+
One rectangular envelope does not represent a sloping ceiling accurately. Record the different heights and use a method that models the actual shapes instead.
Sources and method.
Sources checked on .
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