CALCULATION METHOD
How much flooring do I need?
Multiply each rectangular section’s length by width, add the areas, subtract excluded spaces, and apply a cutting allowance. For boxed flooring, divide the order area by the square-foot coverage printed on the carton and round up.
Gross area = length × width × room count + additional area
Net area = gross area − excluded area
Order area = net area × (1 + waste allowance)
Cartons = order area ÷ carton coverage, rounded up
Pieces = order area ÷ piece face area, rounded up
20 × 15 ft flooring example
A 20 × 15 ft room has 300 sq ft of floor. With a 10% allowance, plan for 330 sq ft. Flooring that covers 20 sq ft per carton requires 17 cartons, providing 340 sq ft of purchased coverage.
Flooring box calculator
Coverage varies by product and décor, so use the square footage printed on the exact carton. Rounding up whole cartons often produces slightly more purchased coverage than the selected allowance. Keeping unopened compatible material can also help with future repairs, subject to the retailer’s return policy and storage requirements.
Plank and tile flooring calculator
Piece mode calculates the face area of one plank or tile and converts the result to both pieces and cartons. It is useful when a product lists dimensions and pieces per box, but carton coverage from the label remains the preferred ordering value when available.
Sheet vinyl and roll flooring calculator
Roll mode divides order area by available roll width and rounds to the selected linear purchase increment. This is only an area estimate: room geometry, roll direction, seams, patterned repeats, damaged edges, and minimum order rules can materially increase the required length.
How much extra flooring should I buy?
The calculator starts at 10%. Home Depot recommends 5–10% extra for many square-footage projects, while diagonal layouts and complex patterns can need more. Use the flooring manufacturer’s waste guidance and the installer’s layout.
The Home Depot square-footage guide for rectangular-section measurement and a 5–10% general allowance; Lowe’s wood and laminate project planner for carton coverage, 10% allowance, and underlayment planning. Accessed September 11, 2026.