A tape measure is enough to start
Room size matters. Glass, sun, people and equipment can matter just as much. Capture the six measurements below and you will have a much better first conversation with an installer.
Open the free room plannerMeasure the longest usable length and width in metres, then measure floor to ceiling. Multiply length by width for floor area. Multiply that area by ceiling height for room volume. For L-shaped rooms, divide the floor into rectangles and add their areas.
Measure the visible width and height of each window and glazed door. Multiply width by height, then add the areas. Large glazing can add far more summer heat than a small difference in floor area.
Use a phone compass or map to identify north, east, south or west. Morning sun affects east-facing glass. South-facing glass receives long periods of sun. West-facing glass can drive late-afternoon overheating.
Record external shutters, awnings, trees or overhangs separately from curtains and internal blinds. Note whether the room is well insulated, average, poor or unknown, and whether it sits directly below the roof.
Record the usual number of people, computers, televisions and kitchen equipment. Use electrical watts from equipment labels where available. The planner treats these as heat released into the room.
Do not multiply one bedroom result across the whole home. Room direction, roof exposure and use differ. Map rooms separately, then compare whether single splits or a multi-split system deserve a quote.
Apple RoomPlan can reduce manual work by detecting walls, windows, doors, openings and approximate dimensions. It is most useful for capturing several rooms consistently. It does not replace the questions about sun, construction or occupancy.
Map rooms manually or import a scan →Ask the installer to show how their room-by-room heat-gain calculation differs from your screening result. The final equipment capacity should come from that design, not a square-metres-only rule.
Record both. Floor area is useful for comparison, while room volume captures the effect of ceiling height. A proper heat-gain estimate also needs windows, direction, shade, people, equipment and the building fabric.
Floor area gives a rough starting point but can miss major differences between a shaded bedroom and a west-facing glass room. Use it for screening, not final equipment selection.
Include open areas that share the room air. Measure large closed cupboards separately if they are normally shut and do not need conditioning.
A LiDAR-equipped iPhone or iPad can use a native RoomPlan app to capture room geometry. You should still confirm windows and thermal details before calculating the cooling load.