How many cubic meters does your room have? Check in 10 seconds
You are sizing an air conditioner, a heat-recovery unit or a heater. The salesperson asks: how many cubic meters? Not square meters (that is the floor), but room volume, meaning how much air fits inside. Your unit's power, your monthly bills and whether it actually keeps the room cool in summer all depend on that one number.
Type the length, width and height of the room (in meters). The calculator returns the volume (m³) and the floor area (m²) in one step. The room does not have to be a rectangle, the L-shape mode lets you add a second rectangle (a kitchen nook, a bay window, a recessed corner).
Advanced mode adds a whole-home sum: you add each room separately, you can exclude a closet or an unheated garage from the total, and you see the cubic meters of the entire space at once. You then drop the result into our ventilation calculator, AC calculator or heating calculator, links sit right under the result.
How to use it
- Measure the room with a laser tape or a regular one. Type the length (longest wall), width (shorter wall) and height (floor to ceiling) in meters. A typical apartment ceiling is 2.5 - 2.7 m, older buildings often 3 - 3.5 m.
- The result shows two numbers: floor area (m², good for lease contracts, flooring, paint) and volume (m³, what you need for ventilation, AC and heating).
- If the room is not a rectangle (an open kitchen with an island, a bay window, an L-shaped living room), pick L-shape. You add a second rectangle: length and width of the part that sticks out. The height stays the same for the whole room.
- Switch on advanced mode to calculate a whole apartment or house. Add each room separately (up to 10), name them (bedroom, living room, bathroom) and watch the total on the bottom card.
- Each room has an "include in total" switch (Apple Switch). Turn it off for spaces you do not want to count, like an unheated garage or a storage closet, useful when sizing ventilation.
- Drop the m³ result straight into the ventilation calculator (sizing a recovery unit), the AC calculator (BTU and kW) and the heating calculator (heating load). Links wait under the result card.
When this is useful
Five situations where a cubic-meter number is the decision, not decoration:
- Sizing an air conditioner for the living room. The seller asks for cubic meters because BTU and kW power scale with volume. 30 m³ fits a 9,000 BTU unit, 60 m³ needs 12,000 BTU, 100 m³ wants at least 18,000 BTU. Get one class wrong and the room will not cool down on a 35°C day.
- Designing mechanical ventilation or HRV. The standard expects 0.5 to 1 air change per hour. A 200 m³ apartment needs 100 to 200 m³/h of airflow, that is what your HRV unit must push. You cannot pick a unit without the volume.
- Calculating a heating load. A heat pump, a gas boiler, a wood stove with a water jacket, every single decision starts with building volume. An old house with 3.2 m ceilings needs more heat than a modern flat with the same floor area.
- Checking whether an air purifier keeps up. The manufacturer quotes CADR in m³/h. Divide CADR by your room volume and you know how many times per hour it filters the room. Allergy sufferers want at least 5 air changes per hour, a casual user is fine with 3.
- Planning a move or storage. Moving companies quote in m³, and furniture is typically 30-40% of the room volume. A 200 m³ apartment is 60-80 m³ of stuff to truck, that decides the container or van size.