What is room air volume?
The air volume of a rectangular room is the total amount of space inside it, measured in cubic metres (m³). It is a fundamental figure for sizing heating, cooling and ventilation systems, estimating air changes per hour (ACH), and working out how quickly a space heats up, cools down, or refreshes its air.
How to use this calculator
Enter the three interior dimensions of the room — its length, width and ceiling height — in metres. The calculator instantly multiplies them together to give the air volume, and also reports the floor area so you can cross-check the room footprint.
The formula explained
For any box-shaped (rectangular cuboid) room the volume is simply the product of the three perpendicular dimensions:
$$V = L \times W \times H$$Because each dimension is a length in metres, multiplying all three gives a result in cubic metres. If your measurements are in different units (for example feet), convert them to metres first for a metric result.
Worked example
Consider a living room that is 5 m long, 4 m wide and 2.5 m high. The air volume is:
$$V = 5 \times 4 \times 2.5 = 50 \text{ m}^3$$with a floor area of \(5 \times 4 = 20 \text{ m}^2\).
If your ventilation target is 3 air changes per hour, you would need a fan moving \(50 \times 3 = 150 \text{ m}^3\) of air every hour.
FAQ
Does this work for any room? It works for any rectangular (box-shaped) room with a flat ceiling. For sloped or L-shaped rooms, split the space into rectangular sections and add the volumes.
What if I measured in feet? Convert each dimension to metres (1 ft ≈ 0.3048 m) before entering, or the result will be in cubic feet instead of cubic metres.
Why is floor area shown too? Floor area (\(L \times W\)) is handy for flooring, paint and quick sanity checks against the volume figure.
