How much flooring do I need to buy?
Type the room’s length and width, the waste allowance and the coverage of one carton. The flooring calculator shows how many square feet to buy, how many cartons that is, and what it costs.
- Flooring to buy (ft²)
- 198
Buy 198 ft² of flooring for 180 ft² of floor.
- Flooring to buy (m²)
- 18.39
- Floor area (ft²)
- 180
- Floor area (m²)
- 16.72
- Cartons
- 10
- Area in the cartons (ft²)
- 200
Flooring to buy (ft²): 198. Buy 198 ft² of flooring for 180 ft² of floor.
How to calculate
Computes a room’s floor area, the flooring to buy with a waste allowance, the number of cartons, and the cost, for laminate, vinyl plank, hardwood or tile.
Example with the default inputs (Room length 15 ft, Room width 12 ft, Waste allowance 10%, Coverage per carton 20 ft²): Buy 198 ft² of flooring for 180 ft² of floor.
Method: Floor area = length × width + other area; flooring to buy = floor area × (1 + waste ÷ 100); cartons = flooring to buy ÷ coverage per carton, rounded up; cost = area paid for × price per ft².
- Waste is 10% by default (Bruce: the usual starting point for a straight plank layout; Lumber Liquidators: 7% to 10% straight, 15% diagonal, 15% to 20% herringbone).
- A carton covers 20 ft² by default; type the coverage printed on your carton.
- The room is a rectangle; add closets and alcoves as other area.
Worked examples
Each example is checked against the calculator on every build.
- Room length 15 ft, Room width 12 ft, Waste allowance 10%, Coverage per carton 20 ft², Price per square foot $3.50 gives Floor area (ft²) 180, Flooring to buy (ft²) 198, Cartons 10, Area in the cartons (ft²) 200, Cost $700.00.Source: Bruce, How to Buy Flooring (length × width; ten percent is the usual starting point for a straight plank layout), https://www.bruce.com/en-us/resources/how-to-buy-flooring-a-guide-for-homeowners.html
- Room length 15 ft, Room width 12 ft, Other area 24 ft², Waste allowance 15%, Coverage per carton 22.5 ft² gives Floor area (ft²) 204, Flooring to buy (ft²) 234.6, Cartons 11, Area in the cartons (ft²) 247.5.Source: Lumber Liquidators, Estimating Your DIY Flooring Project (straight lay add 7–10%; diagonal add 15%), https://lumberliquidators.com/blogs/flooring-inspiration-education/estimating-your-diy-flooring-project
- Room length 16.4 ft, Room width 13.12 ft, Waste allowance 10%, Coverage per carton 23.68 ft² gives Floor area (m²) 20, Flooring to buy (m²) 22, Cartons 10, Flooring to buy (ft²) 236.806029.Source: NIST Handbook 44 (2026), Appendix C (1 ft² = 0.09290304 m²), https://www.nist.gov/document/2026-nist-handbook-44-appendix-c
How it works
- Floor area = length × width + other area (if you type one)
- Flooring to buy = floor area × (1 + waste ÷ 100)
- Cartons (when you type a coverage per carton) = flooring to buy ÷ coverage per carton, rounded up to a whole carton
- Area in the cartons = cartons × coverage per carton
- Cost (when you type a price per square foot) = area in the cartons × price per ft²; with no carton coverage, flooring to buy × price per ft²
- Square metres = square feet × 0.09290304 exactly.
Exact arithmetic. Each size is read as the exact decimal you typed, in the unit you typed it in (12 ft 6 in is exactly 150 in). When you type in a unit, the page stores the size in metres (or square metres) and reads it back as the decimal with the fewest significant digits, in one of the box's units, that gives the same stored number (a feet-and-inches pair counts by its value in inches; on a tie the first unit in the menu wins). When no decimal of up to 17 significant digits in those units gives the stored number (a value that was not typed on the page), the stored number's own shortest decimal, in metres or square metres, is used. Every step is an exact fraction, so 198 ÷ 20 is exactly 9.9 and rounds up to 10 cartons.
Output format. Areas show with at most 2 decimals, cartons as a whole number, and the cost in dollars and cents, each rounded half up from its exact value, with trailing zeros left off. In Metric the answer leads with square metres.
Assumptions
- Waste: 10% by default (Bruce’s starting point for a straight layout); from 0% to 50%.
- Coverage per carton: 20 ft² by default; type the number on your carton. From 0.01 m² to 100,000 m².
- The room is a rectangle; lengths are more than 0 and at most 1,000 m. Other area and the coverage per carton are each from 0.01 m² (0.108 ft²) to 100,000 m².
Worked examples by hand
A 15 × 12 ft room, 10% waste, 20 ft² cartons, $3.50 per ft². 15 × 12 = 180 ft²; × 1.1 = 198 ft²; 198 ÷ 20 = 9.9, so 10 cartons = 200 ft²; 200 × $3.50 = $700.
The same room plus a 24 ft² closet, laid diagonally (15%), 22.5 ft² cartons. 180 + 24 = 204 ft²; × 1.15 = 234.6 ft²; 234.6 ÷ 22.5 = 10.43, so 11 cartons = 247.5 ft².
A 5 × 4 m room, 10% waste, 2.2 m² cartons. 5 × 4 = 20 m²; × 1.1 = 22 m² (22 ÷ 0.09290304 = 236.81 ft²); 22 ÷ 2.2 = 10 cartons.
Other questions people ask
How do I calculate how much flooring I need?
Multiply the room’s length by its width for the floor area, add closets and alcoves, then add a waste allowance. A 15 × 12 ft room is 180 ft²; with 10% waste, buy 198 ft².
How much extra flooring should I buy for waste?
About 10% for a straight layout. Bruce calls 10% the usual starting point for a straight plank layout; Lumber Liquidators says 7% to 10% for a straight lay, 15% for diagonal, and 15% to 20% for herringbone or other patterns, plus 3% to 5% more for rooms with many obstacles.
How many cartons of flooring do I need?
Divide the square feet to buy by the coverage printed on the carton and round up. 198 ft² ÷ 20 ft² per carton = 9.9, so buy 10 cartons.
How do I measure an L-shaped room?
Split it into rectangles. Type the largest one as the length and width, and add the rest as other area. Measure closets and hallways separately too.
Why keep spare flooring after the job?
Leftover planks or tiles from the same lot match the floor in color and finish, so you can replace a damaged piece later. The rounding up to a whole carton usually leaves a few spare pieces.
How do I work out the cost?
Type the price per square foot. The calculator multiplies it by the area in the cartons you buy (whole cartons), or by the flooring to buy when you leave the carton size empty.