Flooring Calculator

How to use this flooring calculator

1. Measure each room wall to wall at floor level. Enter it as a rectangle. For an L-shaped room, enter two rectangles that don’t overlap. Use a triangle for an angled corner.
2. Pick your layout. A straight lay adds 10%, a diagonal layout 15%, and herringbone 20%. Choose “my own extra” if your flooring’s install guide gives a different number.
3. Enter how much one box covers. It’s printed on the box and the product page, usually in square feet per carton.
4. Tick “Add underlayment” if your flooring needs a separate pad, and enter how much one roll covers.
5. Tick “Add baseboard or quarter-round” for trim. Enter the room perimeter, or let the calculator add up the outlines of your areas, and count the doorways.

The result rounds up to whole boxes and tells you how much will be left over. The cost uses example prices that you can change.

How the calculator works

floor area     = sum of every rectangle and triangle
with extra     = floor area × (1 + overage %)
boxes          = with extra ÷ square feet per box, rounded up
underlayment   = floor area ÷ square feet per roll, rounded up
trim (ft)      = perimeter − 3 ft per doorway
trim pieces    = trim × 1.10 ÷ piece length, rounded up

The overage pays for the cut ends at every wall, the pieces you trim around door jambs and vents, and the occasional plank with a flaw you’d rather not use. Manufacturers set it in their install guides. Pergo’s instructions for its Extreme rigid vinyl plank call for 10% extra on a standard installation and 15% on a diagonal one. Bruce asks for 5% on its 3/4 inch solid hardwood, 10% for diagonal floors, and 10% to 15% for glue-down. We use Pergo’s numbers because they’re the more cautious pair.

Herringbone is harder to pin down. Shaw’s installation guidelines for its herringbone flooring say only that herringbone, diagonal, and bordered floors need more than its usual 5% cutting allowance, without naming a number. Our 20% is an estimate. Every row of a herringbone floor ends in an angled cut at the wall, and the short pieces can’t be reused the way straight-lay offcuts can.

Underlayment uses the bare floor area, because it’s rolled out wall to wall and seams butt or overlap only slightly. For trim, the calculator subtracts 3 feet for each doorway and adds 10% for corner cuts and short leftovers, which is our estimate. If you let it add up your areas, it uses the outline of each rectangle and treats triangles as right triangles, so enter the perimeter yourself when two areas share a wall.

A worked example

Say your living room is L-shaped: a 16 × 12 main area with an 8 × 6 dining nook off one side. You’re laying vinyl plank straight, and each box covers 20 square feet.

• Main area: 16 × 12 = 192 square feet
• Nook: 8 × 6 = 48 square feet
• Floor: 240 square feet, plus 10% = 264 square feet
• Boxes: 264 ÷ 20 = 13.2, so 14 boxes, which cover 280 square feet
• Left over after cuts: about 16 square feet

For trim, measure around the walls instead of adding the rectangles. The outline of this L-shaped room is 68 feet, while the two rectangles add up to 84 because the edge they share gets counted twice. With two doorways that’s 62 feet of baseboard. Add 10% and divide by 8-foot pieces to get 9 pieces.

If you switched to a herringbone pattern, the same room would need 288 square feet, or 15 boxes.

Boxes for common room sizes

Boxes of flooring for one rectangular room, with 20 square feet per box:

Your boxes may cover more or less than 20 square feet, so use the calculator with your own number before you order.

Tips for buying flooring

• Buy every box at once and check that the lot numbers match. Pergo and Bruce both tell installers to mix planks from several open boxes, so small color differences spread out across the floor.
• Keep at least one unopened box after the job. If a plank gets damaged later, a matching replacement may be hard to find.
• Leave the expansion gap the instructions ask for. Pergo Extreme needs 1/4 inch at every wall, and the baseboard or quarter-round covers it.
• Install cabinets before a floating floor, not on top of it.
• Count transitions too. Doorways into rooms with different flooring need a threshold or transition strip, sold by the piece.
• Painting the walls before the new floor goes down? The paint calculator handles several rooms at once. For a bathroom or entry in tile, use the tile calculator.