How to use the flooring calculator
- Measure each room at its longest and widest points, wall to wall. Include closets you're flooring, and the floor under doorways up to where the transition strip will sit. If several rooms are the same size, enter one and set the number of rooms.
- Split odd shapes. For an L-shaped room or an open plan, add up rectangles with the square footage calculator, then enter the total area here.
- Choose a waste allowance for your layout (see the table below).
- Enter the coverage per box from the carton. This varies a lot between products — plank size, thickness and brand all change it — so don't rely on the default of 20 sq ft.
The flooring formula
Boxes = floor area × (1 + waste %) ÷ sq ft per box, rounded up
Underlayment rolls = floor area × (1 + waste %) ÷ sq ft per roll, rounded up
Flooring is sold by the full box, so the area you actually buy is boxes × sq ft per box — usually a bit more than the area with waste. The calculator applies material price to the area you buy, and installation price to the floor area, since installers usually charge by the square foot of floor.
Worked example: a 15 × 12 ft living room in laminate
The floor is 15 × 12 = 180 sq ft. With 10% for a straight lay, that's 198 sq ft. At 20 sq ft per box, 198 ÷ 20 = 9.9, so buy 10 boxes (200 sq ft). Underlayment in 100 sq ft rolls: 198 ÷ 100 = 1.98, so 2 rolls.
Laid in herringbone with 15% waste, the same room needs 207 sq ft, and 207 ÷ 20 = 10.35 → 11 boxes.
Waste allowance by layout
| Layout or situation | Typical extra |
|---|---|
| Straight lay, simple rectangular room | 5–10% |
| Rooms with closets, angles, or many doorways | 10% or more |
| Diagonal | 15% |
| Herringbone or chevron | 15–20% |
Solid hardwood is often sold in random lengths, and you'll cut out boards with defects, so many installers lean toward the upper end. Some flooring makers state a recommended allowance in their installation guide; if yours does, use it.
Flooring types at a glance
| Type | Usual installation | Underlayment |
|---|---|---|
| Laminate | Floating, click-lock | Usually needed unless a pad is pre-attached; a vapor barrier is typically required over concrete |
| Vinyl plank (LVP / SPC / WPC) | Floating click-lock, or glue-down | Many have an attached pad; adding a second one can void the warranty — check first |
| Engineered hardwood | Floating, glue-down or nail-down | Depends on the method; floating installs normally need one |
| Solid hardwood | Nail-down over a wood subfloor | Typically a felt or paper underlayment rather than foam |
Underlayment rolls commonly cover about 100 sq ft, but sizes vary — enter the figure on the roll you're buying.
Before and during installation
Acclimation
Wood and wood-based floors expand and shrink with humidity. Most manufacturers ask you to let the boxes sit in the room, at normal living temperature and humidity, before installing — commonly 48 hours or more for laminate, and often longer for solid hardwood. Some rigid-core vinyl products need little or no acclimation. Follow the instructions for your specific product, because ignoring them can void the warranty.
Expansion gap
Floating floors and hardwood need a gap around the edges — at walls, cabinets, pipes and door frames — so the floor can move. It's typically about 1/4 to 1/2 in (6–12 mm), hidden by baseboard or quarter-round. Check the installation guide for the exact figure.
Doorways and transitions
Plan a transition strip wherever the new floor meets a different floor or height: T-molding between floors of equal height, a reducer down to a thinner floor such as vinyl sheet, and an end cap or threshold at sliding doors. Many floating floors also need an expansion break at doorways or across very long runs; the maximum run length is in the installation guide. Undercut door casings so the planks slide underneath for a cleaner finish.
Tips
- Check lot numbers and buy all your boxes at once, so color and gloss match.
- Open several boxes and mix planks as you go to avoid patches of similar color or grain.
- Keep a spare box. Floating floors can have damaged planks swapped out later, but only if you have matching stock.
- Tiling a bathroom or entry instead? Use the tile calculator.
Frequently asked questions
How many boxes of flooring do I need?
Multiply the room's length by its width, add 5–10% for waste (15% or more for diagonal or herringbone), and divide by the square feet per box on the carton. Round up to a whole box. A 15 × 12 ft room with 10% waste and 20 sq ft boxes needs 10 boxes.
How much extra flooring should I buy?
Usually 5–10% for a straight layout in a simple room, 10% or more for rooms with closets and angles, and 15–20% for diagonal or herringbone patterns.
How many square feet are in a box of laminate or vinyl plank?
It varies widely with plank size and thickness — often somewhere around 15–30 sq ft per box. Always use the figure printed on the box you're buying.
Do I need underlayment for vinyl plank?
Many vinyl plank products have a pad attached and don't need (or allow) a separate underlayment. Products without a pad may need one. Check the manufacturer's instructions, as the wrong underlayment can void the warranty.
How big a gap should I leave at the walls?
Typically about 1/4 to 1/2 in (6–12 mm), covered by baseboard or quarter-round. The installation guide for your floor gives the exact figure.