Plank Calculator

Plank Calculator for flooring, decking and plank walls. Enter the room size, plank length and face width to see the planks to buy, the row count, the last-row rip and the job cost.

Plank Calculator for Floors, Decks and Wall Boards

The Plank Calculator works out how many planks to buy for a floor, a deck or a plank wall. It lays the room out row by row, so the count reflects real rip cuts, end cuts and reused offcuts. It is built for DIYers laying hardwood, laminate or vinyl plank, and for anyone decking or cladding with boards of one length.

Enter the room length and width in feet, then the plank length and face width in inches. Face width is the part you see once the floor is down, so leave out the tongue. Measuring across the tongue overstates the coverage of every row, and the count comes up short.

Pick which way the planks run and how they are priced. The accordion holds the gap between planks, the wall gap, the end-joint stagger and a percentage for defects. Somerset's installation guide, which follows the NWFA 2019 guidelines, calls for 3/4 inch of expansion space at walls for solid flooring. Floating floors often use less, so check the product's own instructions.

The row count comes from the width left after both wall gaps are taken off. Each row covers one face width plus one gap, and the last row needs no gap after it.

$$R=\lceil \frac{W+g}{w+g}\rceil$$

W is the width to cover in inches, w is the plank face width and g is the gap between planks. The last row gets whatever width remains after the full rows are placed.

$$w_L=W-(R-1)(w+g)$$

With the defaults, a 12 by 10 foot room loses 3/4 inch at each wall, leaving 118-1/2 inches to cover. Five inch planks need 24 rows, and the last one is ripped to 3-1/2 inches.

Row-by-Row Counts in the Plank Calculator

Most flooring estimates divide area by plank size and add 5% to 15%. Cavalieri Flooring's waste guide, for example, reserves 5% for simple rectangular rooms and 15% or more for diagonal work. That lumps cut waste and spare planks into one guess.

This tool counts the cut waste directly. Each row starts with a full plank, a cut piece or a leftover offcut, then runs full planks and ends with a cut to fit. An offcut is reused to start a later row only when it is at least as long as your stagger.

For the default room, that plan needs 72 planks with 2.3% cut waste, about 2.7 square feet. The 5% defects allowance adds 4 spares for 76 planks. An area rule of 120 square feet plus 10% would have asked for 80.

Stagger is the shortest distance allowed between end joints in neighboring rows. The NWFA installation guidelines call for at least 6 inches on strip flooring, 8 to 10 inches on 3 to 5 inch plank and 10 inches on plank wider than 5 inches. They also say to avoid H patterns, where end joints in nearby rows line up.

The tool checks each new starting cut against the two rows before it, so joints don't repeat every other row. With 48 inch planks and an 8 inch stagger, rows start at 48, 32 and 16 inches before the pattern repeats. If the stagger is more than half the plank length, no starting cut can satisfy it, and the tool warns you.

The Row-by-Row Cut Plan lists every row's start piece, full planks and end piece, marking which pieces are offcuts. Switch Offcuts to Full Plank Each Row for a deck of full-length runs. The third card then shows how many planks the change costs.

Ripping a Thin Last Row

The first card reports rows, planks per row and the last row's rip width. Family Handyman notes that most manufacturers treat a last row under half a plank wide as too narrow. The fix is to rip both the first and last rows to the average of a full plank and the leftover.

Take the same room with 7-1/4 inch planks. That gives 17 rows with a 2-1/2 inch last row, less than half of 7-1/4. The tool tells you to rip the first and last rows to 4-7/8 inches each instead.

Some manufacturers set a hard minimum as well. Johnson Hardwood's engineered flooring guidelines say not to finish with a rip narrower than 2 inches at the far wall. If you would, rip down the first row.

Turning the Planks 90 Degrees

The second card reruns the layout with the planks turned. In the default room, turning them costs one more plank, 77 against 76, and leaves a 2-1/2 inch last row.

Direction is not always free. Somerset's guide, following NWFA, says solid flooring goes perpendicular to the floor joists, or at 45 degrees or more, unless the subfloor is upgraded. Running parallel to joists typically needs a second layer of at least 15/32 inch plywood or bracing between the joists.

For that plywood layer, the Plywood Calculator counts the sheets. Wide solid floors also need room to move across the grain, and the Wood Movement Gap Calculator sizes that gap.

Pricing Planks by the Piece, Foot or Square Foot

Price Quoted takes a price per plank, per linear foot or per square foot of face. The fourth card totals every plank you buy, spares included. The defaults come to $456.00, or 304 linear feet of plank.

The per-square-foot figure on that card divides the cost by the area actually covered, not the room's footprint. The default room covers about 117.3 square feet after wall gaps, so the planks cost $3.89 per square foot of finished floor. That is the number to compare between products.

Solid boards from a lumber yard are usually priced by the board foot instead. Work out that rate with the Board Foot Calculator, then convert it to a price per plank before entering it here.

Before You Order Planks

How many extra planks should I buy?

More than the tool's defects allowance only if the room is irregular. D and G Flooring notes that wider boards waste more, estimating about 12% over for 7 inch planks in a 12 by 14 foot bedroom against about 8% for 5 inch planks. Most of that difference is the rip on the last row.

Because the tool already counts rips and end cuts, the extra percentage only needs to cover defects, mis-cuts and a few repair planks. Order everything from one lot, since planks from a later batch may not match in color or width.

Should deck boards have a gap between them?

Usually, but it depends on moisture. Danny Lipford of Today's Homeowner advises a 1/8 inch gap for pressure-treated boards that were kiln-dried after treatment. Wet treated boards are butted tight because they shrink as they dry.

Enter the gap you will actually install with, since the gap changes the row count. Across 10 feet of 5-1/2 inch boards, 1/8 inch gaps add up to about 2-5/8 inches, roughly half a board. Composite and PVC boards follow each manufacturer's own spacing.

Can I start the next row with the offcut?

Yes, and that is how the tool keeps waste low. Start each new row with the piece cut off the end of an earlier row, as long as it meets your stagger. Pieces shorter than the stagger are scrapped because they would crowd the joints.

Many laminate and vinyl instructions also set a minimum end-piece length, often 8 inches. If the plan shows short end pieces, the tool flags them. Changing the first row's starting cut usually lengthens them.