Flooring & Tile
Flooring Calculator
Enter your room dimensions in feet to get the square footage of flooring to buy and the number of boxes, with a wastage allowance for cuts and spares.
Formula tested · Local units · No sign-up
Project inputs
Enter measurements
Use your preferred units. Results update automatically.
Show the calculation methodFormula, conversions, rounding, and assumptions+
Room area = length × width in square feet — a 12 ft × 10 ft room is 120 sq ft. For L-shaped rooms, add the rectangles and use direct-area mode.
A wastage allowance is added on top (default 8% for a straight plank lay; more for diagonal or herringbone), then the total is divided by the coverage printed on the box — commonly around 20 sq ft per box for laminate or vinyl plank — and rounded up to whole boxes, because flooring is sold in sealed boxes.
Real-world example
Worked example: 12 ft × 10 ft bedroom, vinyl plank, 8% wastage
- Room area: 12 × 10 = 120 sq ft.
- Add 8% wastage: 120 × 1.08 = 129.6 sq ft to purchase.
- Boxes at 20 sq ft per box: 129.6 ÷ 20 = 6.48.
- Round up to whole boxes: 7 boxes.
Buy 7 boxes (140 sq ft). At an example price of $55 per box with 8% sales tax, that's $385.00 + $30.80 = $415.80.
Before you start
How to measure
- Measure the room's length and width in feet at the longest and widest points, including closet floors and doorway thresholds the flooring will run into.
- Take the coverage per box straight from the box label — it varies by plank size and brand, so the ~20 sq ft figure is only a typical starting point.
- For rooms with angles or multiple alcoves, split the floor into rectangles, add the square footage, and enter it in direct-area mode.
Local guidance
Notes for United States
- US flooring is priced per square foot but sold by the box; the box label states both the sq ft coverage and the plank dimensions.
- Vinyl plank (LVP), laminate and engineered hardwood dominate the DIY market; solid hardwood is usually sold by the sq ft through specialty suppliers.
- Sales tax varies by state and locality and is entered manually; big-box shelf prices are per sq ft before tax, so multiply by the box coverage to compare with a per-box quote.
Quick reference
Typical wastage allowance by laying pattern (planning values)
| Pattern | Typical allowance |
|---|---|
| Straight lay, regular room | 8% |
| Straight lay, many doorways/alcoves | 10% |
| Diagonal lay | 12–15% |
| Herringbone / chevron | 15–20% |
Planning values only — your installer and the room's shape determine the real allowance.
Good to know
Common mistakes to avoid
- Ordering the exact room area with no wastage — every row ends in a cut, and you'll want matching spares for future repairs.
- Comparing a per-sq-ft price against a per-box price without multiplying by the box coverage.
- Forgetting closets, pantries and doorway transitions when measuring.
- Using the straight-lay allowance for a herringbone pattern that consumes far more in angled cuts.
Need help?
Frequently asked questions
How many boxes of flooring for a 15 × 12 room?
15 × 12 = 180 sq ft; with 8% wastage that's 194.4 sq ft. At 20 sq ft per box, 194.4 ÷ 20 = 9.72, so buy 10 boxes — and check your actual box coverage, which varies by product.
How much extra flooring should I buy?
8% is the usual planning allowance for a straight lay in a regular room; go to 10% with many doorways or alcoves and 15% or more for diagonal or herringbone patterns. Unopened boxes can often be returned — keep a few spare planks either way.
Does this include underlayment?
No — underlayment is sold separately by the roll (some plank products have it pre-attached). This calculator estimates the flooring itself; the same square footage tells you how much underlayment to buy.
Keep planning
Related calculators
Transparency
About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-16
- Formula version:
- 1.0.0
- Region reviewed for:
- United States
- Spotted an error?
- Report a correction
Methodology
- Room area comes either from length × width or from a directly entered area. All arithmetic runs internally in SI units (m²); regional units (feet, ft²) are converted exactly on the way in and out.
- The area to purchase = room area × (1 + wastage %). Wastage covers end-of-row cuts, defects and spares, and depends mainly on the laying pattern — the default 8% suits a straight plank lay.
- When you enter the coverage per box from the box label, boxes = purchase area ÷ box coverage, rounded UP to a whole box, because flooring is sold in sealed boxes.
- The cost estimate uses the price you enter: price per box × boxes when a box price is given (it takes precedence), otherwise price per area × the purchase area; the tax rate you enter is then applied. No prices are built in.
- The formula is covered by automated unit tests, including hand-calculated worked examples, and is versioned (see formula version on this page).
Sources & standards
- Unit definitions: 1 ft² = 0.09290304 m² (exact definition).
- Wastage allowances: 8% straight lay / 15%+ herringbone are standard planning allowances; confirm with your installer.
This tool provides a material estimate for planning purposes only. It is not a quotation, and it does not cover underlay, trims, subfloor preparation or installation. Confirm quantities and box coverage with your flooring supplier before ordering.