A square footage calculator finds the area of a room or space in square feet from its length and width. Formula: Area = length x width x max(1, rooms). A 12 ft by 15 ft room is 180 sq ft.
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How to use the square footage calculator
- Enter the length in feet.
- Enter the width in feet.
- Enter the number of identical rooms.
- Read the area in square feet.
How the square footage calculator works
The square footage calculator finds the area of a rectangular room or space in square feet. You enter the length and width in feet and, optionally, how many identical rooms there are. It multiplies:
- Area = length × width × number of rooms
Length and width must be positive. The number of rooms defaults to 1. The result is shown in square feet to two decimal places.
Square footage calculator worked example
A bedroom is 12 ft by 15 ft. The square footage calculator returns 12 × 15 = 180 sq ft. Three identical 10 × 10 offices total 300 sq ft. For measurements in feet and inches, convert inches to decimal feet first: 11 ft 6 in is 11.5 ft, so a 14 ft by 11 ft 6 in room is 14 × 11.5 = 161 sq ft.
| Length | Width | Rooms | Sq ft |
|---|---|---|---|
| 12 ft | 15 ft | 1 | 180 |
| 10 ft | 10 ft | 3 | 300 |
| 14 ft | 11.5 ft | 1 | 161 |
| 20 ft | 25 ft | 1 | 500 |
| 12 ft | 12 ft | 4 | 576 |
L-shaped and irregular rooms
Split the space into rectangles, find each area and add them. An L-shaped room made of a 12 × 15 section and an 8 × 6 section is 180 + 48 = 228 sq ft. For a triangle, take half of base × height; for a circle, π × radius². Subtract areas you do not want to count, such as a built-in closet.
Measuring accurately
Measure wall to wall at floor level, rounding to the nearest inch. Take two measurements of each side if the room may not be square, and use the larger for buying materials. Write down each measurement as you go. A laser measure is quick for large rooms.
Using square footage for materials
Flooring, carpet, tile and paint are all priced by area. Add a waste allowance: about 5% to 10% for straight flooring layouts and 10% to 15% for diagonal tile or rooms with many corners. Carpet is often sold by the square yard; divide square feet by 9 to convert. For walls, multiply the room perimeter by the ceiling height and subtract doors and windows.
Square footage of a home
Listings usually report finished, heated living area measured from the outside of exterior walls, and they often exclude garages and unfinished basements. Different measuring standards exist, so two figures for the same house can differ. The square footage calculator gives the floor area of the spaces you measure, which is right for materials but may not match a listing.
Converting units
One square foot equals 144 square inches or about 0.0929 square metres. To change square metres to square feet, multiply by 10.7639. An acre is 43,560 sq ft.
The rooms field
Enter a whole number of identical rooms from 1 to 1,000. The tool rejects zero, negatives and fractions such as 2.5, so the result is always a whole multiple of one room. For rooms of different sizes, run the square footage calculator for each and add the results.
Estimating cost
Multiply the area by the price per square foot. For 180 sq ft of flooring at $4.50 per square foot plus 10% waste, you need about 198 sq ft, which costs about $891 before installation. Ask installers whether their quotes include underlayment, trim and removal of old flooring, since those are often priced separately.
Tips
- Convert inches to decimal feet before entering.
- Split irregular rooms into rectangles.
- Add waste before buying flooring.
- Keep a record of each room’s area for future projects.
Related converters and calculators
Related calculators:
- Area calculator: shapes
- Tile calculator: tiles
- Acres to square feet: land
- Roofing calculator: roof area
Pricing a project by area? Try the deck cost calculator or the drywall calculator.
Sources
OpenStax Prealgebra 2e, 9.4: Rectangles, triangles and trapezoids; NIST: SI units – length.
Formula and method
Area (sq ft) = length (ft) × width (ft) × number of identical rooms. Inches: sq ft = length (in) × width (in) ÷ 144.
Rectangular sections only. Rooms multiplies identical L x W sections.
Questions about this calculator
How do I calculate square footage?
Multiply length by width in feet.
How do I handle inches?
Divide inches by 12 and add to the feet.
How do I measure an L-shaped room?
Split it into rectangles and add them.
How many square feet are in a square yard?
9.
Does it add waste?
No; add 5% to 15% yourself.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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