Volume Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
The volume of a rectangular space is found by multiplying its length, width, and height. Example: a 4 m × 3 m room with a 2.5 m ceiling has a volume of 30 m³.
Explanation
A room's volume is used in particular to size a heating or air-conditioning system (the power needed depends directly on the volume to be heated, not just the floor area), or to estimate a concrete requirement for formwork. For a room with a sloped ceiling (under a roof pitch, for example), this calculation gives an approximation using the average height: for a precise result, break the space down into simpler volumes (a rectangular box plus a triangular prism for the slope) and add them together. For just the floor area, without height, see our area calculator.
Example: a 4 m × 3 m × 2.5 m room
Inputs
Length: 4 m. Width: 3 m. Height: 2.5 m.
Calculation
Volume = length × width × height = 4 × 3 × 2.5 = 30 m³.
Result
This room has a volume of 30 m³.
Frequently asked questions
Why does volume matter for choosing heating or air conditioning?
Because it's the volume of air to be heated or cooled that determines the power needed, not just the floor area. Two rooms with the same floor area but different ceiling heights (2.5 m versus 4 m in a loft) don't have the same requirements.
How do I calculate the volume of a room with a sloped ceiling?
This calculator assumes a flat ceiling. For a slope (under an attic roof), break the space down into a rectangular box (constant minimum height) and a triangular prism for the sloped part, calculate each volume separately, then add them together.
What's the difference between area and volume?
Area (m²) measures a two-dimensional extent (length × width), useful for a floor or a wall. Volume (m³) adds the third dimension, height, and measures a three-dimensional space.