How do I find the square footage of an irregular room?

Split it into rectangles at the corners, measure each, and add them. For a bay window use a triangle or half a circle; for a curved wall use the circle line with the diameter.

How many square feet in a square yard?

Nine. Carpet is often priced per square yard: divide square feet by 9.

Do I measure inside or outside?

For flooring, paint and tile, measure inside wall to wall. For siding, roofing and lot sizes, measure the outside. Round up to the nearest inch.

Square footage calculator

Form 80 · Materials estimateFigures checked 2026-09-04

US customary

Measurements

Rectangle 1 length(ft)

Rectangle 1 width(ft)

Rectangle 2 length(ft)

Rectangle 2 width(ft)

Rectangle 3 length(ft)

Rectangle 3 width(ft)

Circle diameter(ft)

Triangle base(ft)

Triangle height(ft)

What you need

Quantity · Amount

01Rectangle 112 × 14 ft168 sq ft
02Total area168 sq ft
03In square yards9 sq ft per sq yd18.7
04In acres43,560 sq ft per acre0 acres

Prices — put in what you were quoted

Price($ per sq ft)Per square foot, for a materials or labour quote; 0 to skip

Where these figures come from

Plane geometry; 9 sq ft per sq yd and 43,560 sq ft per acre by definition.

Break the space into rectangles and add each one; use the circle and triangle lines for round patios and gable ends. The sheet totals square feet, converts to square yards and square meters, and multiplies by a price per square foot if you enter one, for flooring, sod or paint quotes.

Worked examples

L-shaped room: 12 × 14 plus 6 × 8: 216 sq ft — total area.
Round patio 16 ft across: 201 sq ft — total area.

How it is worked out

Rectangle = length × width. Circle = π × (diameter ÷ 2)². Triangle = base × height ÷ 2. Add the parts. Square yards = ÷ 9; acres = ÷ 43,560; square meters = × 0.0929.

The figures behind it

Plane geometry; 9 sq ft per sq yd and 43,560 sq ft per acre by definition.

Every figure here is an estimate. Materials vary with moisture, compaction and product; order a little extra and confirm quantities with your supplier.

Questions people ask

How do I find the square footage of an irregular room?: Split it into rectangles at the corners, measure each, and add them. For a bay window use a triangle or half a circle; for a curved wall use the circle line with the diameter.
How many square feet in a square yard?: Nine. Carpet is often priced per square yard: divide square feet by 9.
Do I measure inside or outside?: For flooring, paint and tile, measure inside wall to wall. For siding, roofing and lot sizes, measure the outside. Round up to the nearest inch.

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