Square footage calculator

Multiply a room’s width by its length and you have its square footage. Enter the two measurements below and you will get the area in square feet and square metres, along with the perimeter — the number you actually need for skirting, coving and paint.

How to work out square footage

For a rectangular room it is width × length. A room that is 12 ft by 12 ft is 144 sq ft; one that is 10 ft by 12 ft is 120 sq ft. If you measured in metres, multiply the same way and you have square metres — multiply that by 10.764 to get square feet.

Measure at floor level rather than at waist height, and measure the longest and widest points. Walls are rarely perfectly parallel, so if the two ends of the room differ, take the larger figure when you are ordering materials and the smaller one when you are checking whether furniture fits.

Rooms that are not rectangles

An L-shaped room is the usual culprit. Split it into two rectangles, work out each one, and add them together. Bay windows, chimney breasts and alcoves are the same idea: treat each as its own small rectangle and add or subtract it.

Once there is more than one or two of those, splitting rectangles by hand gets error-prone. Draw the room in the planner instead — give each wall its real measurement and the area is calculated from the shape itself, however awkward it is.

Which number do you need for what?

  • Floor area — flooring, carpet, underfloor heating, rugs.
  • Perimeter — skirting board, coving, and the starting point for wall area.
  • Wall area — perimeter × ceiling height, for paint and wallpaper. The paint calculator does this for you.

Common questions

How many square feet is a 12x12 room?
144 square feet, which is 13.38 square metres. A 12 ft by 12 ft room has a perimeter of 48 ft (14.63 m).
How do I convert square metres to square feet?
Multiply square metres by 10.764. Going the other way, multiply square feet by 0.0929. A 20 m² room is roughly 215 sq ft.
Should I include cupboards and alcoves in the floor area?
For flooring, include anything you will lay floor across and exclude fitted units that sit on the subfloor. For a general sense of room size, most people quote the area between the walls and ignore built-in storage.
Do I need to add extra for waste?
Not to the room area itself — that figure should be the real size of the room. Add waste when you order materials instead, usually 10% for flooring and 15% for anything laid diagonally or in a pattern.

Next: how much flooring you need or how much paint.