Room Area Calculator

How to use the room area calculator

1. Fill in the fields — they start with a worked example.
2. Read the answer, and the arithmetic shown beneath it.
3. Copy the results, or adjust the inputs to compare scenarios.

About this tool

Three figures, because different jobs need different ones. Floor area sizes flooring and underfloor heating. Wall area sizes paint and wallpaper. Volume sizes heating, cooling and ventilation — a radiator or air conditioner is specified against the air in the room, not the floor beneath it.

The perimeter is included because skirting, coving and beading are bought by length, and it is the measurement people most often forget to take while they have the tape out.

Both unit systems are shown throughout, since the trade rarely agrees with itself: rooms get measured in metres, timber gets sold in feet, and radiators get specified in watts against a volume in cubic metres.

For an irregular room, split it into rectangles, calculate each and add them. That is more reliable than trying to measure an L-shape directly, and it is what a surveyor would do.

Common uses

• Getting square footage for an estate agent or listing.
• Sizing a radiator or air conditioning unit by volume.
• Measuring for skirting board and coving.

Frequently asked questions

How do I calculate an irregular room?

Split it into rectangles, work out each separately and add them. That is more accurate than measuring an L-shape as one figure.

Why does volume matter?

Heating, cooling and ventilation are sized against the air in a room. A tall room needs more heat than its floor area alone suggests.

Do I measure to the plaster or the studs?

To the finished surface for paint and flooring. Structural work uses different references, so check what the specification asks for.