Square Footage Calculator

How to use the Square Footage Calculator#

1. Choose a shape. Pick rectangle, triangle, circle or trapezoid.
2. Enter the measurements. Choose your unit first, then type each side.
3. Add a cost. Optional. Enter a price per square foot for a total.

The area formulas#

A room 20 feet long and 15 feet wide has an area of 300 square feet. If the flooring costs 3.50 a square foot, the cost is 1,050 before waste.

Allow for waste#

Add 5 to 10 percent to your area when you buy materials, to cover cuts, mistakes and spares. Diagonal tile layouts and patterns need more. One square metre is 10.764 square feet.

Common sizes and conversions#

Useful conversions: 1 square yard is 9 square feet, 1 square metre is 10.764 square feet and 1 acre is 43,560 square feet. In Nigeria, plots are often sold in square metres, so switch the unit above if your measurements are in metres.

Worked examples for each shape#

A room measures 12 ft by 15 ft, so the area is 180 sq ft. A triangular gable with a base of 24 ft and a height of 9 ft has an area of ½ × 24 × 9 = 108 sq ft. A circular patio with a radius of 8 ft covers π × 8² = 201.1 sq ft. A trapezoid-shaped plot with parallel sides of 40 ft and 60 ft and a height of 30 ft covers (40 + 60) ÷ 2 × 30 = 1,500 sq ft. If you measure in metres, the calculator converts: a 4 m by 5 m room is 20 m², which is 215.3 sq ft.

Ordering materials: add waste#

Never order exactly the area you measured. Flooring and tiles are cut at the edges, and some pieces break. A usual allowance is 5 to 10 percent for plain layouts and up to 15 percent for diagonal patterns or rooms with many corners. For a 180 sq ft room with 10 percent waste, order 198 sq ft. Paint is different: one US gallon covers roughly 350 sq ft of wall for one coat, so work out the wall area, not the floor area, and subtract large windows and doors. Always check the coverage printed on the tin.

Square footage in property listings#

Real estate figures are not always comparable. Some listings count only the living area inside the walls, others include garages, balconies or the thickness of the walls. Ask what is included, and measure for yourself if a decision depends on it. Prices per square foot or square metre help you compare, so enter a cost per sq ft in the calculator to see the total. Land is often measured in acres, which is 43,560 sq ft, and the calculator shows that figure too. The rent calculator helps when you compare monthly costs.

Estimating tiles#

To tile a 180 sq ft floor with 12 × 12 inch tiles, each tile covers 1 sq ft, so you need 180 plus waste. At 10 percent, order 198 tiles, rounded up to the next full box. For a 24 × 12 inch tile, each covers 2 sq ft, so the count is 90 plus waste. Check the coverage per box, since boxes are sold in fixed amounts, and buy extra from the same batch, as colours vary slightly between production runs.

Measuring odd rooms#

For an L-shaped room, extend one wall to split it into two rectangles, measure each and add the areas. If the main part is 14 × 12 ft and the extension is 6 × 5 ft, the area is 168 + 30 = 198 sq ft. A built-in cupboard comes off the total: work out its area and subtract it. For a bay window or a curved wall, measure the widest points and add a small allowance.

Measure twice, because small errors in length multiply when you work out an area. Write the numbers on a sketch and keep it with you when you shop for materials.

Last reviewed October 2026 by the Calclulo team.