How to measure square footage
Square footage is length times width, both in feet. A room 12 ft by 14 ft is 168 sq ft.
Worked example. A room 12 × 14 ft.
- Area: 12 ft × 14 ft = 168 sq ft
- In square yards: 168 ÷ 9 = 18.67 sq yd
- In square metres: 15.61 m²
Measure along the floor, wall to wall, and write feet and inches as they are on the tape: the calculator reads 12' 6", 12.5 and 150 in as the same length, and shows what it understood beside the field.
A whole house is its rooms added up, or its outline if you can measure it outside: one rectangle of 40 × 30 ft and a wing of 20 × 14 ft come to 1,480 sq ft. Give each area a name and the table under the drawing lists them, room by room, with the total. “Copy” puts that list in a message.
- L-shaped rooms. Measure the main part, then the part that sticks out. A room 20 × 12 ft with an extension of 8 × 6 ft is 288 sq ft.
- Closets and alcoves. Add each as an area of its own.
Odd shapes
- Circles. The distance across the middle, squared, times 3.1416, divided by 4. A circle 10 ft across is 78.54 sq ft.
- Triangles. Half the base times the height, measured square to the base: 10 ft by 6 ft is 30 sq ft.
- Trapezoids. A room with one slanted wall, or a bay window: the two parallel sides added, halved, times the distance between them. Sides of 10 ft and 6 ft, 5 ft apart, make 40 sq ft.
- Anything else. Cut it into these on paper, and add them.
The drawing shows every area to one scale, so a 14 ft side typed as 41 stands out before it is ordered.
Walls or floors
A floor is covered by its area: flooring, tile and carpet are bought by the square foot or the square yard of floor. Paint, drywall and wallpaper go on walls, and a wall’s area is its length times its height.
For the walls of a whole room, choose “Walls of a room”: the length of the walls all the way round, their height, and the area of the doors and windows to take away. A room 12 × 14 ft has 52 ft of wall; at 8 ft high, less 45 sq ft of openings, that is 371 sq ft.
Sheets and boards are another count: the drywall calculator turns walls and ceilings into sheets.
Square feet, square yards and square meters
Stores do not agree on a unit. Flooring and tile are priced by the square foot, carpet often by the square yard, and anything from a metric country by the square metre.
| From square feet | Divide by |
|---|---|
| To square yards | 9 |
| To square metres | 10.76 |
| To acres | 43,560 |
Going the other way, 4 × 5 m is 20 m², which is 215.28 sq ft. The calculator gives all four at once, and takes metres and centimetres as readily as feet: switch the units, or just write 4 m.
Questions about square footage
How do I calculate the square footage of a room?
Multiply its length by its width, in feet. Inches are a twelfth of a foot each: 12 ft 6 in is 12.5 ft.
How many square feet in a square yard?
9: a yard is 3 ft, and 3 × 3 is 9. A room of 168 sq ft is 18.67 sq yd.
How do I measure an L-shaped room?
As two rectangles: the main part, and the part that sticks out. Measure each, and add them. The calculator’s L-shape asks for exactly those four sides.
How many square feet in an acre?
43,560. A lot of 100 × 150 ft is 15,000 sq ft, or 0.34 acres.
Sources
- National Institute of Standards and Technology, Guide to the SI (Special Publication 811), Appendix B.9: conversion factors. A foot is 0.3048 m and an inch 2.54 cm, exactly. A cubic foot is 0.02831685 m³, a cubic yard 0.7645549 m³, a US gallon 3.785412 L, a square foot 0.09290304 m² and an acre 4,046.873 m². Read on .
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