How it works
The calculator multiplies the length and width of each rectangle, adds the results, and then subtracts the areas you list as left out.
Total = Σ (Length × Width) for every rectangle
Left out = Σ (Length × Width × How many) for every cut-out
Net area = Total − Left out
Square yards = Square feet ÷ 9 · Square meters = Square feet × 0.09290304
All lengths are converted to one internal unit before multiplying, so you can type one side in feet and the other in inches or meters. Nothing is rounded until the result is displayed.
Measuring a room
Measure at floor level, wall to wall, along the line where the new floor will run. Walls are rarely perfectly straight, so take the length at two or three points and use the largest figure – a small overestimate costs less than a missing row of planks. Write down each measurement as you go, with a sketch of the room, and label every rectangle so you can check the numbers later.
Doorways count when the floor continues through them. If the new floor stops in the middle of a door opening, add a narrow rectangle for that strip: for example 3 ft wide and 2 in deep.
Rooms that are not rectangles
An L-shaped room is two rectangles. Draw one straight line that cuts the L into two parts, measure each part up to that line and enter them as two rows. A T-shaped or U-shaped room is three rectangles. The drawings under the calculator show each of the first three rectangles to scale, so you can see whether the sizes you typed are plausible.
For a diagonal corner, measure the room as if the corner were square and list the missing triangle as a cut-out of half its size: a corner triangle with two 3 ft legs is half of a 3 × 3 ft square, so enter it as 3 × 1.5 ft. Curved walls are best approximated by a few narrow rectangles.
Which areas to leave out
List only the areas the new material will not cover. Common examples are kitchen islands, built-in cabinets and vanities, a fireplace hearth, a shower base or a closet that keeps its old floor. If several cut-outs have the same size, enter the size once and set how many there are. Freestanding furniture and most appliances stay in the area, because the floor normally runs under them.
What to do with the result
The net area is the starting point for every flooring estimate. To turn it into boxes, rolls or bags, use the calculator for the material: tile and grout, laminate or vinyl plank boxes, carpet by the roll width, or wall paint for the walls of the same room. Those calculators let you enter the area directly and add the waste allowance and package size that apply to your product.
Contractors and stores quote in different units. Carpet is often priced per square yard, most hard flooring per square foot, and imported products per square meter, so the result is shown in all three. One square yard is exactly 9 sq ft, and one square foot is exactly 0.09290304 m², because the international foot is defined as 0.3048 m.
Worked example
Inputs
- Rectangles to measure 1
- Length 12 ft, Width 10 ft
- Rectangles to measure 2
- Length 8 ft, Width 6 ft
Result
- Total of the rectangles
- 168 sq ft
- Areas left out
- 0 sq ft
- Net area
- 168 sq ft (18.67 sq yd, 15.61 m²)
Common mistakes
- Overlapping rectangles. When you split an L-shaped room, draw the dividing line once and measure each part only up to that line – otherwise the corner is counted twice.
- Mixing feet and inches by hand. 12 ft 6 in is 12.5 ft, not 12.6 ft. Type it as 12 ft 6 in and let the calculator convert it.
- Leaving out closets and alcoves. If the flooring runs into a closet, add the closet as its own rectangle.
- Subtracting something you will actually cover. Flooring usually runs under freestanding appliances and furniture; only leave out areas that stay uncovered.
- Treating the net area as the amount to buy. Flooring, carpet and tile are sold in whole boxes or rolls and need extra for cuts – use the matching material calculator for that.
Assumptions and limits
- Every row is a rectangle – length × width. Diagonal walls, curves and bay windows have to be approximated with rectangles or measured separately.
- Cut-outs are rectangles too, and are subtracted from the total of all rows, not from one particular room.
- The result is a plain area. It includes no waste allowance and no rounding to packages.
- Conversions use exact factors. 1 ft = 0.3048 m, so 1 sq ft = 0.09290304 m², and 1 sq yd = 9 sq ft.
Frequently asked questions
How do I calculate the square footage of a room?
Measure the length and the width in feet and multiply them. A room 12 ft by 10 ft has 12 × 10 = 120 sq ft. If a side is not a whole number of feet, convert the inches first – 6 in is 0.5 ft – or type the measurement as 12 ft 6 in and the calculator does it for you.
How do I measure an L-shaped room?
Split it into two rectangles along one line and measure each part separately, stopping at that line. Enter each rectangle as its own row. A room made of a 12 × 10 ft part and an 8 × 6 ft part has 120 + 48 = 168 sq ft.
How many square feet are in a square yard?
Nine. A yard is 3 ft, so a square yard is 3 × 3 = 9 sq ft. Carpet is often priced per square yard, so the calculator shows both.
How do I convert square feet to square meters?
Multiply by 0.09290304, the exact factor that follows from 1 ft = 0.3048 m. 168 sq ft is about 15.61 m². To go the other way, divide square meters by 0.09290304 – 19 m² is about 204.5 sq ft.
Should I subtract the area under cabinets?
Only if the flooring will not go there. Fixed base cabinets and kitchen islands are often installed before the floor and left out; check the installation instructions of the floor you plan to buy before deciding.
Does this calculator add waste?
No. It gives the measured area only. The tile, laminate, vinyl plank and carpet calculators add a waste allowance you set and round up to whole boxes or rolls.
Sources
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 3, 2026