How the calculator works it out
Each shape gets its own area in square feet. The calculator adds them up, converts the total to square yards and square meters, then adds your waste allowance and multiplies by the price if you entered one.
Rectangle: length × width
Triangle: base × height ÷ 2
Circle: 3.1416 × (diameter ÷ 2)²
Trapezoid: (side a + side b) ÷ 2 × height
Square yards = square feet ÷ 9 · Square meters = square feet × 0.09290304
For the trapezoid, side a and side b are the two parallel sides, and the height is the straight-line distance between them, not the length of a slanted side. For a triangle the height is measured square to the base, from the base to the far point.
Worked example: an L-shaped living room
The main part of the room is 12 ft by 10 ft and the dining nook is 8 ft by 6 ft. That is 120 + 48 = 168 square feet, which is 18.67 square yards or 15.61 square meters. Laminate at $3.50 per square foot with 10% extra comes to 168 × 1.10 = 184.8 square feet to buy, or $646.80. This is the example loaded when the page opens.
How to measure an L-shaped room
- Sketch the room and mark the inside corner of the L.
- Draw an imaginary line from that corner straight to the opposite wall. You now have two rectangles that do not overlap.
- Measure the length and width of each rectangle, wall to wall.
- Enter each one as a rectangle above. The calculator adds them.
The same trick works for T-shaped and U-shaped rooms: keep cutting until every piece is a rectangle, triangle or circle. BuildDirect's guide to measuring a floor recommends the same approach, including measuring the open areas around a kitchen island as separate pieces.
Which shape to use
| Space | Shape | What to measure |
|---|---|---|
| Most rooms, decks, slabs | Rectangle | Length and width |
| A corner cut off at 45° | Rectangle plus triangle, or trapezoid | The two parallel walls and the distance between them |
| A gable wall above the eaves | Triangle | Base width and peak height |
| Round patio or fire pit area | Circle | Diameter, through the middle |
| Bay window floor | Trapezoid | Back wall, front edge and depth |
Waste allowance for flooring
You lose material to cuts at walls, doorways and corners. BuildDirect suggests at least 5% for a simple install, 10% for rooms with several obstructions and 15% for triangular rooms. Patterned layouts such as diagonal or herringbone waste more again. The installation guide for your product is the final word, and it is worth keeping a box or two for future repairs since dye lots change.
Unit conversions used
One foot is exactly 0.3048 meters, as defined by NIST, so one square foot is exactly 0.09290304 square meters. One square yard is 9 square feet. Inches are divided by 12 before anything is multiplied, so mixing feet and inches never introduces rounding errors.
Questions people ask
How do I find the square footage of a room?
Measure the length and width in feet and multiply them. A 12 ft by 14 ft bedroom is 12 × 14 = 168 square feet. If the room is not a plain rectangle, split it into rectangles, work each one out and add them together.
How do I measure an L-shaped room?
Draw a line across the inside corner so the L becomes two rectangles. Measure each rectangle separately and add the areas. A 12 × 10 ft space plus an 8 × 6 ft alcove is 120 + 48 = 168 square feet. Make sure the two rectangles do not overlap, or you will count that floor twice.
How much extra flooring should I buy?
BuildDirect suggests at least 5% for a simple do-it-yourself install, 10% for rooms with several obstructions and 15% for triangular rooms with lots of diagonal cuts. Diagonal or herringbone layouts waste more than straight ones. Check the installation guide for your product, since some manufacturers state their own figure.
How do I convert square feet to square yards or square meters?
Divide square feet by 9 to get square yards, because a yard is 3 feet and 3 × 3 = 9. Multiply square feet by 0.09290304 to get square meters. That factor is exact: one foot is defined as 0.3048 meters, and 0.3048 squared is 0.09290304.
How do I measure in feet and inches?
Choose "ft + in" above and type the feet and the leftover inches in separate boxes, such as 11 ft 7 in. The calculator converts 7 inches to 7 ÷ 12 = 0.583 ft, so 11 ft 7 in is 11.583 ft. Do not type 11.7, which means 11 feet and 8.4 inches.
Do I subtract kitchen islands and built-in cabinets?
For flooring that goes under nothing fixed, yes: measure the island and leave it out, or measure the open floor around it as separate rectangles. For paint, real estate listings or heating calculations, people usually use the full room size.