Floor area is the number everyone asks for - the headline figure on a listing, the basis of a quote, the line on a planning form. Get it wrong and you mislead a buyer or under-price a job. This guide explains how floor area is measured, the difference between the common standards, and how to get an accurate area straight off a plan you scanned or drew on your phone.
What "floor area" actually means
There's no single number called "the area" - it depends on where you draw the line. The two you'll meet most are gross internal area (GIA), measured to the inside face of the external walls, and net internal area, which excludes structural walls, stairwells, and the like. RoomPlot calculates a gross internal floor area by taking the wall centrelines and offsetting them to the inner faces - a RICS/BOMA-style method - so the figure reflects the usable footprint rather than the outer shell.
Get the area off the plan
Once a room is enclosed, RoomPlot detects it and calculates its area for you - no manual sums. The room-by-room breakdown updates as you edit the walls, and a project total rolls up from the individual rooms. You can read every figure in metric or imperial, and switching the project between the two converts every area at once.
- Automatic detection finds each enclosed room and tags its area at the centre.
- Manual override lets you set an exact value when you need precise control or a measured figure to match.
- Report area selection lets you rename an area, exclude one, or add a report-only area (loft, store, balcony) that isn't a full scanned room.
Tip. Always state which standard you measured to. "24.6 m² GIA" tells a surveyor or agent exactly what they're looking at; a bare number invites argument. RoomPlot's calculation is RICS/BOMA-style gross internal area - say so in your report.
Put areas in a report
For a client deliverable, RoomPlot's multi-page report adds a Room/Area Summary - per-room rows with a bold project total - plus an "All Floors Area" figure on the cover for multi-storey jobs. You can rename areas, override individual values, and add manual report-only spaces from a quick presets list, so the schedule reads exactly how your trade expects.
Common mistakes to avoid
- Mixing standards. Don't compare a GIA figure with a net internal one - they answer different questions.
- Measuring to the outer wall. Usable area is to the inner face; the outer line overstates it.
- Forgetting to label units. 24.6 means nothing without m² or sq ft next to it.
Frequently asked questions
Does RoomPlot calculate area automatically?
Yes. Each enclosed room gets an auto-calculated area, and you can override it manually when you need an exact figure.
Which area standard does it use?
A gross internal area measured from wall centrelines offset to the inner faces - a RICS/BOMA-style method. State that in your report so the reader knows what the number means.
Can I show all the areas in one place?
Yes. The multi-page report includes a room-by-room area summary with a project total and an all-floors figure on the cover.
Measuring up for a listing or a quote? See how to measure a room or browse more floor-plan guides.
