# How much flooring do I need to buy?

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.

- Page: https://www.acalculator.org/construction/flooring-calculator
- JSON spec: https://www.acalculator.org/construction/flooring-calculator.json
- Version: a71487464aef

## Default answer

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.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Room length | The length of the room, wall to wall. |
| w | Room width | The width of the room, wall to wall. |
| other | Other area | Floor area of closets, a hallway or an alcove to add, measured the same way. Leave empty for none. |
| waste | Waste allowance | Extra flooring for cuts and mistakes, in percent: 10% for a straight layout, 15% for diagonal. |
| box | Coverage per carton | The floor area one carton covers, printed on the carton. Leave empty to skip cartons. |
| price | Price per square foot | What the flooring costs per square foot. Leave empty to skip the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| buy | Flooring to buy (ft²) | The floor area plus the waste allowance, in square feet. |
| buyM2 | Flooring to buy (m²) | The same area in square metres. |
| floor | Floor area (ft²) | Length × width, plus any other area, in square feet. |
| floorM2 | Floor area (m²) | The floor area in square metres. |
| boxes | Cartons | Flooring to buy ÷ the coverage per carton, rounded up to a whole carton. |
| bought | Area in the cartons (ft²) | Cartons × the coverage per carton, in square feet. |
| cost | Cost | The area you pay for (in the cartons, or the flooring to buy) × the price per square foot. |

## 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.

## Assumptions

- 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

1. l = 4.572, w = 3.6576, waste = 10%, box = 1.858061, price = $3.50 gives floor = 180, buy = 198, boxes = 10, bought = 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.
2. l = 4.572, w = 3.6576, other = 2.229673, waste = 15%, box = 2.090318 gives floor = 204, buy = 234.6, boxes = 11, bought = 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.
3. l = 5, w = 4, waste = 10%, box = 2.2 gives floorM2 = 20, buyM2 = 22, boxes = 10, buy = 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.

## FAQ

### 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.

## Sources

- Bruce, How to Buy Flooring: A Guide for Homeowners (measure length by width; ten percent is the usual starting point for a straightforward plank layout; diagonal, patterns and irregular rooms need more). https://www.bruce.com/en-us/resources/how-to-buy-flooring-a-guide-for-homeowners.html (retrieved 2026-10-02)
- Lumber Liquidators, Estimating Your DIY Flooring Project (straight lay add 7–10%; diagonal add 15%; herringbone or complex patterns add 15–20%; rooms with many obstacles add 3–5% more; round up to the nearest carton). https://lumberliquidators.com/blogs/flooring-inspiration-education/estimating-your-diy-flooring-project (retrieved 2026-10-02)
- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement: 1 ft = 0.3048 m; 1 ft² = 0.09290304 m²; 1 yd² = 9 ft². https://www.nist.gov/document/2026-nist-handbook-44-appendix-c (retrieved 2026-10-01)