Deck boards, counted the way you’ll actually rack them — full rows across the width, cut from the board length you can haul.
Deck details
ft
ft
Deck boards to buy (incl. 5% waste)
—
Rows across the deck—
Screws (2 per board per joist @16" OC)—
Deck area—
Assumes standard 5.5-in boards with a 1/4-in gap (one row per 5.75 in). Composite boards often specify their own gap and hidden fasteners — the manufacturer’s chart overrides.
Counting boards like a decker
Boards run one direction; rows stack across the other. A 5.5-inch board plus the standard quarter-inch drainage gap consumes 5.75 inches of width per row. Each row needs enough board length to span the deck — ideally landing butt joints on joists, which is why buying boards that match your deck length (or half of it) saves both cuts and waste.
A 16 × 12 deck with 16-ft boards: 26 rows × 1 board each = 26, call it 28 with waste — every board spans full length, zero butt joints. The same deck from 8-footers needs 55 boards and puts a joint in every row. Fasteners: about 26 rows × 2 screws × 13 joists ≈ 700 screws, or roughly 2 lbs per 100 sq ft.
Small choices that show forever
Crown boards bark-side down, gap consistently (a 16d nail makes a perfect spacer), and pre-drill ends to stop splits. If joints are unavoidable, stagger them across joists in a running pattern — aligned joints read as a stripe across the whole deck from ten feet away.
Frequently asked questions
How many deck boards do I need per square foot?
With standard 5.5-inch boards and a 1/4-inch gap you get about 2.1 linear feet of board per square foot of deck. A 200 sq ft deck is roughly 420 linear feet of decking before waste.
What gap should I leave between deck boards?
About 1/4 inch for dry treated lumber and most composites. Wet ("green") pressure-treated boards shrink as they dry, so they’re often laid nearly tight and the gap appears on its own.
How many screws does a deck take?
Two per board at every joist. With joists 16 inches on center that works out to roughly 350 screws per 100 sq ft — buy the 5-lb box, not the little one.