How to Measure a Room in Square Feet

What you need

A tape measure, paper and a pencil. A laser measure makes long spans easier and one-person measuring much faster, but it is not required.

Sketch the room before you start. Even a rough rectangle with the walls labelled prevents the most common mistake, which is losing track of which number belongs to which wall.

The basic measurement

1. Measure the length. Run the tape along the longest wall, at floor level, from wall to wall.
2. Measure the width. Same again on the perpendicular wall.
3. Multiply them. 14 ft × 12 ft = 168 square feet.

Three details that matter more than they sound:

Measure at the floor. Baseboards and skirting taper outward at the bottom. A measurement taken at waist height can read an inch or two short per wall, which compounds across a room.

Measure wall to wall, not baseboard to baseboard. You are laying flooring up to the wall, under where the baseboard sits.

Take the widest points. Rooms are rarely square, particularly in older buildings. If one wall is 14 ft and the opposite is 14 ft 3 in, use 14 ft 3 in for materials.

Converting feet and inches

Tape measures read in feet and inches; the formula needs decimals. Divide the inches by 12:

Reading	Decimal feet
12 ft 3 in	12.25 ft
12 ft 6 in	12.5 ft
12 ft 7 in	12.583 ft
12 ft 9 in	12.75 ft

So a room 14 ft 6 in by 12 ft 3 in is 14.5 × 12.25 = 177.63 square feet.

The room sqft calculator has a feet + inches mode so you can enter both boxes directly. There is more on this in the inches guide.

Rooms that are not rectangles

L-shaped rooms. Draw a line across the inside corner to split the room into two rectangles. Measure each, then add. Cross-check by measuring the full bounding rectangle and subtracting the missing corner — the two should agree.

Bay windows. A square bay is a small rectangle added to the main room. An angled bay is a trapezoid: average the two parallel sides and multiply by the depth.

Alcoves and recesses. Small rectangles. Add them.

Chimney breasts and columns. Measure the room as though the obstruction were not there, then subtract its footprint. A breast projecting 12 in from a 4 ft wide section is 4 sq ft to subtract.

Curved walls. Approximate with a part-circle, or divide the curve into several short straight segments. See the shapes guide.

What to include

It depends entirely on what the number is for.

Measuring for flooring

• Include closets, alcoves and under-stair spaces you will be flooring
• Include the area under radiators and freestanding furniture
• Exclude built-in cabinetry that sits on the subfloor
• Add a waste allowance afterwards — see the flooring guide

Measuring for a property listing

• Include closets, hallways and landings
• Exclude anything with a ceiling under 7 ft
• Exclude garages and unheated space
• Follow the full conventions in the house square footage guide

Measuring for paint

• You want wall area, not floor area — perimeter × ceiling height
• Subtract doors and windows
• Use the wall and paint calculator

Totalling a whole house

Switch the room calculator to Multiple rooms and add a row per room. The total updates as you go.

Work systematically, floor by floor, and tick each room off your sketch as you enter it. The commonest error in a whole-house measurement is not a bad number — it is a forgotten hallway.

Common room sizes for reference

Room	Typical size	Square feet
Small bedroom	10 × 10 ft	100 sq ft
Standard bedroom	12 × 12 ft	144 sq ft
Master bedroom	14 × 16 ft	224 sq ft
Bathroom	8 × 5 ft	40 sq ft
Kitchen	12 × 14 ft	168 sq ft
Living room	16 × 20 ft	320 sq ft
Single garage	12 × 22 ft	264 sq ft

Useful as a sanity check. If your measurement says a standard bedroom is 400 square feet, re-check the arithmetic before ordering anything.