Square Footage Calculator: Work Out Any Area in Seconds
Every home project starts with the same question: how big is the area? Flooring is priced by the square foot, paint coverage is printed on the tin in square feet, and tile, sod and grass seed are all sold by area — so one wrong measurement quietly multiplies through everything you order. This square footage calculator works out rectangles, squares, triangles and circles, totals several identical areas at once, and adds a waste allowance before you buy. Enter your measurements in feet or metres and you get the area of one shape, the grand total, and the total with waste, in square feet, square yards and square metres.
How to calculate square footage
For a rectangle or a square room, square footage is simply length multiplied by width. Measure at floor level, from wall to wall — skirting boards can hide half an inch on each side, so push the tape into the corners — and if the walls are not perfectly straight, write down the longest length and the widest width. Multiply the two numbers and you have the area: a room 12 ft long and 10 ft wide is 12 × 10 = 120 sq ft.
If your measurements are in inches, there is no need to convert each one by hand. Multiply the inches together first, then divide the answer by 144 — there are 144 square inches in one square foot. A space measuring 150 in by 118 in covers 17,700 sq in, and 17,700 ÷ 144 = 122.92 sq ft. Whichever way you measure, round up rather than down, and when the number is for ordering materials, add a waste allowance on top: cuts, breakages and pattern matching all eat into the pile, and running one box short in the middle of a job costs far more than a small surplus.
Square Footage Calculator
Pick a shape, enter your measurements, and the results update as you type — or press Calculate. Several identical areas and a waste allowance are handled in the same step.
Enter your measurements, then press Calculate.
Formulas: rectangle = length × width; square = side × side; triangle = base × height ÷ 2; circle = π × radius², with radius = diameter ÷ 2. Conversions: 1 sq yd = 9 sq ft; 1 m² = 10.764 sq ft.
L-shaped and awkward rooms
Real rooms are rarely one clean rectangle. An L-shaped living room, a kitchen wrapped around a chimney breast, or a hallway that narrows at the stairs will defeat a single length-times-width measurement — but it breaks down easily. Sketch the floor plan and split it into rectangles: one rectangle for the main body of the L and a second one for the leg. Measure and calculate each rectangle on its own, then add the areas together. That sum is the room's true square footage.
There are two ways to run that split through this tool. If the sections repeat — two identical alcoves, matching bays, the same landing on two floors — enter one section and set the number of identical areas to match, and the tool totals them for you. If every section is different, run the calculator once per section and add the totals; writing each sub-total down as you go keeps the running sum honest. The same approach handles bays and bump-outs: measure the main rectangle, then the extra piece on its own terms — a semicircular bay is half a circle — and add it on.
Square footage formulas for every shape
Every result on this page comes from one of four formulas. Keep them somewhere handy and you can check any quote, delivery note or material estimate in under a minute:
| Shape | Formula |
|---|---|
| Rectangle | length × width |
| Square | side × side |
| Triangle | base × height ÷ 2 |
| Circle | π × radius² (radius = diameter ÷ 2) |
And the conversions this calculator uses: 1 sq yd = 9 sq ft, so divide square feet by 9 to get square yards; and 1 m² = 10.764 sq ft, so divide square feet by 10.764 to get square metres. A worked check with the room above: 120 sq ft is 120 ÷ 9 = 13.33 sq yd, and 120 ÷ 10.764 = 11.15 m² — exactly what the tool reports.
What to calculate next
Square footage is the starting number, not the shopping list. Once you know the area, the next step depends on the job. For laminate, vinyl, hardwood or carpet, the flooring calculator turns an area into boards, packs and underlay. For walls and ceilings, the paint calculator converts area into litres and tins, allowing for extra coats. For ceramic, porcelain or mosaic, the tile calculator works out tile counts, adhesive and grout from the same area. And every other measuring job on this site — mulch, gravel, concrete, decking and more — is gathered on the calculators hub:
- Flooring Calculator — boards, packs and underlay for a floor of any size.
- Paint Calculator — litres and tins for walls and ceilings, coat by coat.
- Tile Calculator — tiles, adhesive and grout for floors and walls.
- All Calculators — the full hub of measuring tools.
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the length by the width, both measured in feet from wall to wall at floor level. A room 12 ft long and 10 ft wide is 12 × 10 = 120 sq ft. For a room that is not a simple rectangle, split the plan into rectangles, work out each area and add them together.
How many square feet are in a square yard?
Nine. A square yard measures 3 ft by 3 ft, and 3 × 3 = 9 sq ft. To convert, divide any square footage by 9 — handy because carpet is still often sold by the square yard.
How do I measure an L-shaped room?
Split the L into two rectangles on paper, measure the length and width of each, multiply them out and add the two areas together. Run this calculator once per rectangle — or use the quantity field when two sections are the same size — and the sum is the room's total square footage.
Should I add extra for waste?
Yes, whenever the area is for ordering materials. Cuts, breakages and pattern matching mean you always use more than the neat area suggests, and 10% is the usual allowance for flooring and tile. Enter it in the waste field above and the tool adds it to your total for you.
Estimates only — measure twice before ordering materials.