How do I convert square feet to square yards, square meters or acres?

Divide square feet by 9 for square yards. Multiply by 0.09290304 for square meters. Divide by 43,560 for acres. All three are exact definitions. Going the other way, multiply square yards by 9, divide square meters by 0.09290304 (about 10.764 sq ft per m²), or multiply acres by 43,560.

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

Break the floor into simple shapes: rectangles, right triangles and circles or half circles. Work out each one, then add them, and subtract any shape that is cut out of a bigger one. Our guide to measuring irregular areas walks through it with examples.

How do I find the square footage of an L-shaped room?

Split the L into two rectangles that do not overlap. Multiply length by width for each and add the two. A 12 by 10 ft section plus a 6 by 8 ft section is 120 + 48 = 168 sq ft. Pick L-shape in the calculator to enter both sections at once.

How do I work out the area of a circle?

Halve the diameter to get the radius, multiply the radius by itself, then multiply by π (about 3.1416). A circle 10 ft across has a 5 ft radius, so 5 x 5 x 3.1416 = 78.54 sq ft. For a half circle, halve the answer.

How do I work out the cost per square foot?

Multiply the area by the price per unit, using the same unit for both. 168 sq ft at a price of P per square foot costs 168 x P. If the price is per square yard, convert first: 168 sq ft is 18.67 sq yd, so the cost is 18.67 x P. If you add extra for waste, price the area including the extra, because that is what you buy. The calculator does this for you when you add a price.

How many square feet are in an acre?

Exactly 43,560. An acre is also 4,046.8564224 square meters, or 4,840 square yards. A square lot of one acre is about 208.7 ft on each side.

Square Footage Calculator: Sq Ft, Sq Yd, m² and Acres

Square footage is the flat area of a floor, wall, yard or lot. Flooring, carpet, tile, paint, sod and land are all priced by it, and every material calculator on this site starts with it. The calculator handles the four shapes that cover most rooms and plots, and converts the answer to square yards, square meters and acres.

How to measure a room

Use a tape measure or a laser measure and work in one unit if you can.

Measure wall to wall along the floor, at the longest point, for the length.
Measure the other direction for the width.
Measure both again near the opposite wall. Rooms are rarely perfectly square; if the two readings differ, use the larger one so you do not come up short.
Write inches as part of a foot. 12 ft 6 in is 12.5 ft, and 12 ft 3 in is 12.25 ft. Or pick "in" from the unit menu and enter 150 in.
Include closets and alcoves you are covering. Measure each as its own rectangle and add them, or use the L-shape option.

For rooms with angled walls, bays or curves, split the floor into rectangles, triangles and circles. Our guide to measuring irregular areas shows how.

The formula for each shape

Rectangle or square: length x width.
Circle: π x radius x radius. The radius is half the diameter, so a circle 10 ft across has a 5 ft radius.
Triangle: base x height ÷ 2. The height is measured at a right angle from the base to the far corner, not along the sloping side.
L-shape: split it into two rectangles that do not overlap, work out each one, and add them. Length x width for the first section, plus length x width for the second.

The calculator converts every measurement to feet first, so you can mix units (one side in meters, the other in feet) and still get the right answer. Then:

square yards = square feet ÷ 9
square meters = square feet x 0.09290304
acres = square feet ÷ 43,560

Worked example: a 12 x 14 room

Area: 12 x 14 = 168 sq ft.
Square yards: 168 ÷ 9 = 18.67 sq yd. Carpet is often priced this way.
Square meters: 168 x 0.09290304 = 15.61 m².

Worked example: an L-shaped room

A living room is 15 ft by 12 ft, with a dining nook 6 ft by 8 ft opening off one side.

First section: 15 x 12 = 180 sq ft.
Second section: 6 x 8 = 48 sq ft. Measure the nook only from where the main rectangle ends, so no floor is counted twice.
Total: 180 + 48 = 228 sq ft, or 25.33 sq yd, or 21.18 m².

The other way to do it is to draw a rectangle around the whole L and subtract the missing corner. Both give the same answer if the measurements are right.

Square feet to acres

One acre is exactly 43,560 square feet. That is a definition, not a rounded figure: NIST lists the acre as 43,560 ft², which is 4,046.8564224 m² using the international foot of exactly 0.3048 m.

To convert, divide square feet by 43,560. A 150 ft by 100 ft lot is 15,000 sq ft, and 15,000 ÷ 43,560 = 0.344 acres. To go the other way, multiply acres by 43,560: half an acre is 21,780 sq ft.

Older US land records used the US survey foot, which NIST retired at the end of 2022. The difference in an acre is a few parts per million, far smaller than any tape measure error.

Conversions this calculator uses

Every factor here is an exact definition, not a rounded estimate.

Conversion	Value	Basis
1 foot	0.3048 m exactly	International yard and pound agreement, 1959 (NIST)
1 square yard	9 sq ft exactly	1 yd = 3 ft
1 square foot	0.09290304 m² exactly	0.3048 x 0.3048 (NIST SP 811)
1 acre	43,560 sq ft exactly (4,046.8564224 m²)	NIST unit conversion factors

Common mistakes

Treating inches as decimals. 10 ft 6 in is 10.5 ft, not 10.6 ft.
Dividing by 3 to get square yards. A square yard is 3 ft by 3 ft, so divide square feet by 9.
Using the diameter as the radius. That makes a circle four times too big. Halve the diameter first, or enter the diameter in the calculator and let it do the halving.
Measuring a triangle along the slope. The height must be square to the base.
Counting the corner of an L twice. Each piece of floor belongs to one section only.
Ordering the bare area. The area is the floor you cover. Materials such as flooring and tile are usually bought with extra for cuts and pattern matching; put your installer's or the manufacturer's figure in the waste field.

Square footage calculator

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