How to use the square footage calculator
- Measure the room at floor level, wall to wall, and type each measurement as feet and inches. 12 ft 6 in goes in as 12 and 6. You can leave inches empty, or type decimal feet such as 12.5 in the feet box.
- Pick the shape. Most rooms are rectangles. Use a triangle for an angled corner, a circle for a round area and a half circle for a curved bay.
- Add another area for every extra room or part of a room. The total adds them all up.
- Optional: under Waste and cost, add a waste percentage and the price per square foot to see how much flooring to buy and roughly what it costs.
Switch to Meters to measure in meters and centimeters instead. The result is always shown in square feet, square meters and square yards, so you can compare prices from any store. Copy result gives you a list of every area and the totals to paste into a message or a quote request.
How square footage is worked out
Each measurement is first turned into feet: inches are divided by 12, so 6 inches is 0.5 ft. Then the area of each shape is:
| Shape | Formula | Example | Area |
|---|---|---|---|
| Rectangle | length x width | 12 ft 6 in x 10 ft 3 in | 128.13 sq ft |
| Triangle | base x height / 2 | 10 ft base, 8 ft height | 40.00 sq ft |
| Circle | 3.14159 x diameter x diameter / 4 | 10 ft across | 78.54 sq ft |
| Half circle | circle area / 2 | 10 ft straight side | 39.27 sq ft |
For the rectangle, 12 ft 6 in is 12.5 ft and 10 ft 3 in is 10.25 ft, and 12.5 x 10.25 = 128.125 square feet. A triangle's height is measured at a right angle to its base, not along the sloping side.
To change square feet into square meters, the calculator uses the exact definition of the foot. The US National Institute of Standards and Technology (NIST) states "1 foot = 0.304 8 meter exactly", so one square foot is 0.3048 x 0.3048 = 0.09290304 square meters. The 128.125 sq ft room above is 11.90 m². A square yard is 3 ft x 3 ft, or 9 square feet, which is how carpet is often priced in the US.
L-shaped rooms and irregular shapes
Split any room with straight walls into rectangles that do not overlap, work out each one, and add them together. That is why the calculator lets you add as many areas as you need.
Take an L-shaped living room. Draw a line across it where the L turns, so you get one large rectangle of 20 ft by 12 ft and one smaller rectangle of 8 ft by 6 ft. Press Try an L-shaped room to see it filled in.
| Part | Size | Square feet |
|---|---|---|
| Area 1 | 20 ft x 12 ft | 240.00 |
| Area 2 | 8 ft x 6 ft | 48.00 |
| Total | 288.00 | |
| With 10% waste | 288 x 1.10 | 316.80 |
| Cost at $3.50 per sq ft | 316.8 x 3.50 | $1,108.80 |
Measure each part only once. If the two rectangles share a strip of floor, the shared strip is counted twice and the total is too big. A room with an angled wall can be split into a rectangle plus a triangle. For a curved bay, choose Half circle and enter the width of the straight side: its area is half that of a full circle.
To leave out something the flooring will not cover, such as a kitchen island, work it out on its own and take it off the total yourself.
How much extra flooring to buy
Flooring is cut to fit at walls, doorways and corners, and some pieces are spoiled. So people usually buy a little more than the floor area. Adding 5 to 10 percent is a common allowance, not a rule. A plain rectangular room with large planks may need less; diagonal tile layouts, patterned carpet and rooms with many corners usually need more.
The best figure is the one the flooring maker or your installer gives for that product and that layout. Enter it under Extra for waste and the calculator adds it to the total. If you also enter a price, the cost is worked out on the area including waste, because that is what you buy.
Flooring is usually sold in whole boxes or rolls of a fixed size. Divide the area with waste by the area one box covers, as printed on the box, and round up to a whole box.
Measuring in meters (UK and elsewhere)
Choose Meters and enter meters and centimeters, for example 4 m 50 cm, or type 4.5 in the meters box. The main result then shows square meters, which is how flooring is priced in the UK, with square feet underneath.
For example, a room 4.5 m by 3.2 m is 14.40 m². Dividing by 0.09290304 gives 155.00 square feet. If you enter a price in metric mode, it is read as a price per square meter.
Questions and answers
How do I calculate square footage with feet and inches?
Turn the inches into a fraction of a foot by dividing by 12, add it to the feet, then multiply length by width. A room 12 ft 6 in by 10 ft 3 in is 12.5 x 10.25 = 128.13 square feet.
How do I find the square footage of several rooms?
Work out each room on its own and add the results. In the calculator, press Add another area for each room; the total updates as you type.
How do I measure an irregular or L-shaped room?
Split it into rectangles, triangles or circles that do not overlap, measure each part and add them together. An L-shaped room is two rectangles.
How much extra flooring should I buy?
Many people add 5 to 10 percent for cuts and mistakes. That is a common allowance, not a rule. Use the figure your flooring maker or installer gives for the product and the layout you chose.
How many square feet are in a square meter?
About 10.764. A foot is exactly 0.3048 m, so a square foot is exactly 0.09290304 m², and one square meter is 1 divided by 0.09290304, which is 10.7639 square feet.
How do I turn square feet into square yards?
Divide by 9, because a square yard is 3 feet by 3 feet. 288 square feet is 32 square yards.
Sources
Checked on 7 October 2026. If a rule has changed, please tell us.