How do I handle a room with a curved or angled wall?

Break it into rectangles that fit inside, then approximate the remainder as a triangle — half the base times the height. For a curve, measure the chord and treat it as a triangle plus a small allowance; the error is smaller than the waste percentage you will add anyway.

Square metres or square feet?

Use whichever your supplier quotes and convert only once, at the end. Converting mid-calculation is where rounding errors creep in. The exact factor is 10.7639 sq ft per square metre.

Square Footage Calculator

Calculate area and cost for flooring, painting, or tiling.

Enter values to see the result.

Measuring floor area in a room that is not a rectangle

Almost no real room is a clean rectangle. The reliable method is to split the floor into rectangles, measure each one, and add them — not to measure the longest wall by the widest point and hope.

How it works

Multiplies length by width for each rectangular section and totals the areas.
Converts between square metres and square feet, since flooring and paint are quoted in both.
Handles subtractions for a chimney breast, a kitchen island or anything else you are not covering.

area = Σ (length × width) for each rectangle

1 m² = 10.7639 sq ft
1 sq ft = 0.0929 m²

an alcove or bay is its own rectangle; a chimney breast is subtracted

Worked example

An L-shaped living room: a 4.2 × 3.6 m main space with a 2.4 × 1.8 m return.

rectangle A = 4.2 × 3.6 = 15.12 m²
rectangle B = 2.4 × 1.8 = 4.32 m²
total = 15.12 + 4.32 = 19.44 m²
in imperial: 19.44 × 10.7639 = 209.3 sq ft
the shortcut of 6.6 × 3.6 gives 23.76 m² — 22% too much

19.44 m², or 209 sq ft. Measuring the bounding box instead would have you buying 22% more flooring than the room can hold — on a 40-per-square-metre floor, about 170 wasted.

Reading the result

Measure at floor level, not at waist height. Walls are rarely plumb, and skirting boards mean the floor is narrower than the room appears. For flooring, the floor dimension is the one that matters.
Take each measurement twice at different points along the wall. A room that is 3.60 m at one end and 3.54 m at the other is completely normal in an older building, and you should work from the larger figure.
Bays, alcoves and door recesses are separate rectangles, not rounding errors. A single bay window can easily add a square metre.
Do not subtract kitchen units or built-in wardrobes if you are laying flooring underneath them, and do subtract them if you are not. Decide before you measure, because it changes the answer by more than the waste allowance does.

Common questions

How do I handle a room with a curved or angled wall?: Break it into rectangles that fit inside, then approximate the remainder as a triangle — half the base times the height. For a curve, measure the chord and treat it as a triangle plus a small allowance; the error is smaller than the waste percentage you will add anyway.
Square metres or square feet?: Use whichever your supplier quotes and convert only once, at the end. Converting mid-calculation is where rounding errors creep in. The exact factor is 10.7639 sq ft per square metre.