Flooring: Plank Rows and Last-Row Width

All versions

Nothing looks worse than a finished floor ending in a two-inch sliver. Before the first plank goes down, work out how many rows the room takes and how wide the last one will be — then decide whether to rip the first row narrower.

Quick formula: Round the row count up, then measure what is left:

=ROUNDUP(B2/C2,0)

A 146-inch room with 7.5-inch planks takes 20 rows, and the last row lands at 3.5 inches — narrow, but workable.

Functions used (tap for the full reference guide):

ROUNDUP

The example

Three rooms, each measured across the direction the planks run.

	A	B	C	D	E
1	Room	Width (in)	Plank (in)	Rows	Last row (in)
2	Living room	146	7.5	20	3.5
3	Bedroom	132	7.5	18	4.5
4	Hallway	44	7.5	6	6.5

The formula

ROUNDUP counts the rows; simple subtraction finds the leftover:

=ROUNDUP(B2/C2,0) // room width over plank width, rounded up to whole rows

How it works

Two numbers decide the whole layout:

B2/C2 gives the exact row count — 146 over 7.5 is 19.47 rows.
ROUNDUP(...,0) makes that 20, because the twentieth row exists even if it is ripped narrow.
=B2-(D2-1)*C2 subtracts the full rows from the room width to reveal the last row: 146 minus 142.5 is 3.5 inches.

Installers generally want the last row at least a third of a plank wide. If it comes out thinner, rip the first row down so the two edges match.

Try it: interactive demo

Interactive

Enter the room width and the plank width, both in inches.

Room width (in)

Plank width (in)

Variations

Balance both edges

Split the leftover between the first and last row so the floor looks symmetrical.

=(B2-(D2-2)*C2)/2

Planks per row

Run the same math along the length to size your order.

=ROUNDUP(F2/G2,0)

Pitfalls & errors

Measure the face width of the plank, not the box width. Click-lock planks lose roughly a quarter inch to the locking edge and your row count will be off.

Leave the expansion gap out of the room width — usually a quarter inch each side — or the last row will be wider on paper than on the floor.

Practice workbook

📊

Download the free Flooring: Plank Rows and Last-Row Width practice workbook

Edit the yellow width cells; rows and the last-row width recalculate.

Frequently asked questions

Why not just round to the nearest row?

Rounding down deletes a row you will physically have to install. ROUNDUP always reflects reality — the last row exists no matter how narrow it is.

Does this replace the square-footage order?

No. This is layout planning; you still order by area plus a waste factor. Use both — area tells you what to buy, rows tell you how it lands.

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Function references: ROUNDUP