How to use this calculator
- Pick the shape of the main area: a rectangle for most rooms, a triangle for an angled corner or gable, or a circle for a round patio or bed.
- Measure the length and width in feet (or metres) and enter them. For a circle, enter the diameter; for a triangle, the base and the height measured square to it.
- For an L-shaped room, closet or bay, enter the length and width of the extra rectangle. Leave both at 0 if the space is a simple shape.
- Enter the area of anything you won't cover, such as a kitchen island or built-in cabinets, and set the number of identical rooms if you have several.
- Set a waste allowance for the material you are buying and enter the price per square foot (or square metre) to see the cost.
How to calculate square footage
For a rectangle, multiply length by width with both measured in feet. A triangle is half of base × height, and a circle is π × diameter² ÷ 4. Irregular rooms are easiest split into rectangles: work out each part, add them together and subtract anything that won't be covered. If a measurement includes inches, divide the inches by 12 first, so 12 ft 6 in becomes 12.5 ft.
Example: an L-shaped living room measures 15 × 12 ft with an 8 × 6 ft dining nook, and a 12 sq ft fireplace hearth won't get new flooring. The area is 180 + 48 − 12 = 216 sq ft, which is 24 square yards or about 20.07 m². With 10% waste you need to buy 237.6 sq ft, and at $4 per square foot the material comes to $950.40.
Metric works the same way in metres. A 4.2 × 3.6 m bedroom is 15.12 m² (about 162.75 sq ft). With 10% waste that is 16.63 m², which costs 748.44 at a price of 45 per square metre. The calculator also shows the perimeter of the main shape, which is handy for baseboard, trim or edging.
Pro tips
- Measure at floor level, wall to wall, and take two readings in long rooms. Walls are rarely perfectly square, so use the larger figure.
- Round each measurement up to the next inch or centimetre. The small extra is far cheaper than a second trip for one more box.
- Sketch the floor plan on paper first and label each rectangle. It makes L-shaped and open-plan spaces much easier to add up without missing a section.
- Include closets and the space under appliances that sit on the finished floor, but leave out kitchen islands and built-in cabinets.
- Carpet is often quoted per square yard. Divide square feet by 9 to convert, or read the square-yard figure straight from the results.
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the length by the width in feet. A 14 × 12 ft room is 168 sq ft. If the room has an alcove or closet, work out that part separately and add it on.
How do I find the square footage of an L-shaped room?
Split it into two rectangles, find the area of each and add them. A 15 × 12 ft room with an 8 × 6 ft nook is 180 + 48 = 228 sq ft. Enter the nook as the extra rectangle in the calculator.
How many square feet is a 10 × 10 room?
A 10 × 10 ft room is 100 sq ft, which is about 11.11 square yards or 9.29 m². Two rooms of that size add up to 200 sq ft.
How do I convert square feet to square metres?
Multiply square feet by 0.0929, or divide by 10.764. For example, 168 sq ft is about 15.61 m², and 15.12 m² is about 162.75 sq ft.
How do I calculate square footage with feet and inches?
Convert the inches to a decimal of a foot by dividing by 12, then multiply. A room 12 ft 6 in × 10 ft 3 in is 12.5 × 10.25 = 128.13 sq ft.
How do I find the area of a circle or triangle in square feet?
For a circle, multiply π by the diameter squared and divide by 4: a 10 ft round patio is about 78.54 sq ft. For a triangle, multiply the base by the height and halve it: a 12 ft base with a 9 ft height is 54 sq ft.
How much extra flooring should I buy?
Add 5–10% for a straight lay of planks or tile, about 15% for diagonal patterns and 20% for herringbone. On a 168 sq ft room, 10% extra means buying 184.8 sq ft.
These results are estimates for planning and budgeting. Actual quantities depend on site conditions, products and workmanship. Check structural and code requirements with a licensed professional before you build.