Area & Volume
Square Footage Calculator
Pick the shape that matches your space, enter the measurements in feet, and get the area in square feet. The same result is shown in square yards, square meters and acres.
Worked example
- Area = 20 x 15 + 10 x 8 = 380 sq ft.
- Square yards = 380 / 9 = 42.22; square meters = 380 x 0.0929 = 35.30.
Common sizes at a glance
| Size | Area | Square yards | Square meters |
|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 11.11 | 9.29 |
| 12 x 12 ft | 144 sq ft | 16.00 | 13.38 |
| 12 x 15 ft | 180 sq ft | 20.00 | 16.72 |
| 20 x 20 ft | 400 sq ft | 44.44 | 37.16 |
| 24 x 36 ft | 864 sq ft | 96.00 | 80.27 |
| 30 x 40 ft | 1,200 sq ft | 133.33 | 111.48 |
The shapes and their formulas
Most spaces in a house are one of four shapes, or several of them joined. The calculator handles each:
- Rectangle: length times width.
- L-shape: two rectangles added together, as in the 20 x 15 plus 10 x 8 example that totals 380 sq ft.
- Triangle: half the base times the height, handy for gables and corner beds.
- Circle: 3.1416 times the radius squared, where the radius is half the diameter.
Breaking up odd spaces
Sketch the space on paper first. Draw lines to cut it into rectangles and triangles, measure each piece, and add the areas. Do not overlap pieces, or that strip gets counted twice. For a notch or a column you will not cover, work out its area and subtract it.
Curved edges, like a round patio border, can be split into a rectangle and a half circle. Half the circle's area covers the curve.
Converting units
One square yard is 9 sq ft, so carpet and some turf sold by the yard use the square yard figure. One square foot is about 0.0929 square meters, useful for products with metric labels. An acre is 43,560 sq ft, which helps when you are planning seed or fertilizer for a lawn. The square yard calculator adds a waste allowance for yard-sold products.
From area to materials
Area is the first step for almost every project on this site. Once you have the number, take it to the flooring calculator for boxes of flooring, or to the concrete slab calculator if you add a thickness. For a single room measured in feet and inches, the room square footage calculator saves the conversion.
Questions
How many square feet is a 12 x 15 room?
180 sq ft, which is 20 square yards.
How do I measure a circle?
Measure straight across the widest point to get the diameter and enter it. The tool halves it and squares the radius for you.
Should I add extra for waste?
Not here. Area is the true size. The material calculators add the waste that fits each product.
How many square feet is an L-shaped room?
Split it into two rectangles that do not overlap, find each area, and add them. The worked example does this: 300 plus 80 is 380 sq ft.
How this works: formulas and typical values are listed on our method page; every data source and its license is on sources.
Last reviewed November 2026.