How to use it
- Enter each room's length and width in feet and the number of doors.
- Choose the layout: straight, diagonal or herringbone.
- Enter the coverage per box, baseboard length and underlayment roll size.
- Add prices if you like and read the materials list.
How it calculates
Floor area is the sum of length × width for every room you add. An L-shaped room is simply two rectangles.
Flooring needed = area × (1 + waste %). Boxes = flooring needed ÷ sq ft per box, rounded up.
Baseboard = the perimeter of each room minus its doorways, plus 5%, divided by the length of one piece. Underlayment = area plus 5% overlap, divided by the roll size.
Example: a 16 × 14 ft living room and a 12 × 11 ft bedroom total 356 sq ft. With 7% waste you need about 381 sq ft, so at 20 sq ft per box that's 20 boxes (400 sq ft). The walls minus two 3 ft doors are 100 ft; with 5% extra, that's 14 pieces of 8 ft baseboard. Underlayment: 374 sq ft, or 4 rolls of 100 sq ft.
Waste allowance by layout
| Layout | Waste |
|---|---|
| Straight (parallel to a wall) | 5–10% (7% default) |
| Diagonal | 12–15% |
| Herringbone | 15–20% |
Pick the higher end for small rooms, many corners, closets and hallways. Keep one spare box for future repairs; a different production lot can differ slightly in color.
Underlayment and moisture
Most laminate needs a foam or cork underlayment unless it has one pre-attached. Over concrete slabs and basements you also need a vapor barrier (6-mil polyethylene or an underlayment with a built-in barrier). Luxury vinyl plank often has an attached pad and may not need extra underlayment; check the manufacturer's instructions, because the wrong underlayment can void the warranty.
If your product doesn't need underlayment, just ignore that line of the results.
Expansion gap and baseboards
Laminate floats and expands with humidity, so it needs an expansion gap of about 1/4 to 3/8 in around the edges (follow the manufacturer). Baseboard or quarter round covers the gap; it doesn't change how much flooring you need.
Baseboard and shoe molding usually come in 8 ft or 16 ft pieces; enter the length you'll buy. Door width defaults to 3 ft. Enter prices per sq ft, per baseboard piece and per underlayment roll to get the total material cost.
Before you buy
- Measure each room wall to wall at its widest points and round up to the next half foot.
- Include closets you'll floor; subtract only large fixed items such as kitchen islands.
- Let the flooring acclimate in the room for the time the manufacturer specifies, usually 48 hours.
- Planks are sold by the box, so the calculator always rounds up to whole boxes.
For tile instead of planks, use the tile calculator.
Frequently asked questions
How much extra flooring should I buy?
About 7–10% for a straight layout, 12–15% for diagonal and 15–20% for herringbone.
How many boxes of laminate do I need for 500 square feet?
With 10% waste you need 550 sq ft. At 20 sq ft per box that's 28 boxes; check the coverage printed on your boxes.
How do I measure an L-shaped room?
Split it into two rectangles and add each as a separate room.
Do I need underlayment for vinyl plank?
Often not if the planks have an attached pad, but check the manufacturer's instructions. Laminate usually needs underlayment.
Does it work for vinyl plank and engineered wood?
Yes. The math is the same for any floating floor sold by the box.
Last updated: November 12, 2026