Square Footage Calculator
Find the area of a room, floor, or wall in square feet, square yards, and square meters. Enter each area's shape and size, and subtract openings such as windows and doors.
Add rooms or areas, or subtract openings such as windows and doors.
- Choose US or Metric. You can still change the unit of any single field, for example inches for a narrow strip of wall.
- Pick the shape of the area and enter its dimensions. For a shape that is not listed, or an area you already know from a floor plan, choose Known area and enter the area directly.
- Use Quantity when several areas have the same size, such as two identical windows.
- Use Add section for each extra area. Set a section to Subtract for parts that do not need material, such as a window in a wall or a kitchen island on a floor.
- Optionally, add a waste allowance and a price per square foot, square yard, or square meter to estimate the cost.
Most rooms and walls can be built from a few sections:
- L-shaped room: add two rectangles, or enter the full rectangle and subtract the missing corner.
- Wall: enter the wall's length as Length and its height as Width, then subtract each window and door.
- Gable wall: add a rectangle for the lower part and a triangle (base and height) for the peak.
Dimension fields accept these formats:
-
Whole numbers and decimals, such as
12or10.5 -
Fractions, such as
3/4 -
Mixed numbers, such as
30 1/2
Choose ft + in as the unit to enter a length such as 12 ft 6 in in two fields. Quantity takes a whole number, and the waste allowance and price take whole numbers or decimals.
How to calculate square feet
The area of a rectangle is:
Area = length × width
Convert both dimensions to the same unit before you multiply. With dimensions in feet, the result is in square feet. A square yard is 3 ft × 3 ft, so divide square feet by 9 to get square yards.
- 1 yd² = 9 ft²
- 1 ft² = 144 in²
- 1 ft² = 0.09290304 m² (1 m² ≈ 10.763910 ft²)
- 1 yd² = 0.83612736 m²
The area of each shape is calculated as follows.
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Circle | π × diameter² ÷ 4 (or π × radius²) |
| Triangle (base and height) | base × height ÷ 2 |
| Triangle (three sides) | Heron's formula: √(s(s − a)(s − b)(s − c)), where s = (a + b + c) ÷ 2 |
| Trapezoid | (parallel side A + parallel side B) ÷ 2 × height |
| Ring | π × (outer diameter² − inner diameter²) ÷ 4 |
| Rectangular border | outer length × outer width − (outer length − 2 × border width) × (outer width − 2 × border width) |
| Known area | the area you enter |
With several sections, the calculator adds the areas of the sections set to Add, subtracts those set to Subtract, and then adds the waste allowance: total = net area × (1 + waste % ÷ 100).
Measuring a room
Measure the length and width of the floor from wall to wall at floor level. You can enter the measurements in feet and inches as they are. Split an L-shaped or irregular room into rectangles and add each one as a section. Include closets and alcoves that will get material.
For a wall, enter its length and height and subtract the windows and doors. For a whole home, measure each room and add it as a section. A home's listed square footage is measured differently, as described in Square footage of a home below.
Examples
A rectangular room
A room 12 ft × 10 ft is 120 ft², which is 13.33 yd² or 11.15 m². With a 10% waste allowance, the total is 132 ft², and at $3.50 per square foot the cost is $462.00.
An L-shaped room
Split the room into a 12 ft × 10 ft rectangle and an 8 ft × 6 ft rectangle: 120 + 48 = 168 ft². You get the same result from a 20 ft × 10 ft rectangle with an 8 ft × 4 ft corner subtracted: 200 − 32 = 168 ft².
A wall with windows and a door
A wall 14 ft long and 8 ft high is 112 ft². Subtract two windows of 3 ft × 4 ft (24 ft²) and a door of 3 ft × 6 ft 8 in (20 ft²). The area to paint or cover is 68 ft², or 7.56 yd².
A gable wall
A wall 24 ft wide with 8 ft sides is 192 ft². The triangle above it, 24 ft at the base and 6 ft high, adds 24 × 6 ÷ 2 = 72 ft², for a total of 264 ft².
Metric dimensions
A room 4 m × 3.5 m is 14 m², or 150.69 ft². With a 5% waste allowance, the total is 14.7 m², and at £25 per square meter the cost is £367.50.
Square footage of a home
This calculator gives the area you measure, which is what you need to buy flooring, tile, or paint. The square footage listed for a home is measured differently. In the United States, Fannie Mae has required appraisals for the mortgages it buys to follow the ANSI Z765-2021 standard since April 1, 2022. Fannie Mae's guidelines summarize it as follows:
- Measure the outside of the exterior walls, and report the total in whole square feet.
- Count only finished areas with a ceiling at least 7 ft high. In a room with a sloped ceiling, at least half of the finished area must be 7 ft or higher, and any part under 5 ft is left out.
- A level that is even partly below ground is reported separately as a basement. Openings to the floor below, such as a two-story foyer, are not counted, and stairs count on the level they go down from.
- Garages are reported separately from the living area.
- Apartment-style condominiums do not use this standard and are measured from the inside.
Listings and tax records do not always follow this standard. Because materials are measured room by room inside the walls, and include closets that get flooring, the area you calculate for materials usually does not match a home's listed square footage.
FAQ
9. A square yard is a square 3 ft on each side, and 3 × 3 = 9.
Multiply the dimensions in inches and divide by 144. For example, 30 1/2 in × 60 in is 1,830 in², or 12.71 ft². You can also choose in as the unit, and the calculator converts it for you.
Split the room into rectangles, triangles, and other shapes, and add a section for each. For a notch or a cut-out, subtract it from a larger shape instead.
Multiply square feet by 0.09290304. The calculator shows the total in square feet, square yards, and square meters at the same time.
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