Deck Calculator
How many boards does a 16×12 deck take? Pick a board profile, set your gap and waste factor, and get the board, screw, and joist counts to take straight to the lumber yard — and to check against a contractor's materials quote.
boards run this way
15% for diagonals
Decking board
Board length (ft)
Boards to buy
29
16-ft boards
Deck area
192
sq ft
Lineal feet
457.6
incl. 10% waste
Board rows
26
across the width
Joists
13
12-ft, 16" OC
Deck screws
≈672
3.5 per sq ft
Assumes boards run parallel to the deck's length, so rows stack across the width. The screw count figures two screws per board at every joist with joists 16" on center — about 3.5 per square foot. Bump waste to 15% for diagonal decking or picture-frame borders, and buy an extra board or two so you can cull crooked stock.
How Deck Board Math Works
The estimate assumes boards run parallel to the deck's length, so rows of decking stack across the width: divide the width by board width plus gap. A 12-ft-wide deck with 5.5" boards and a 3/16" gap needs ceil(144 ÷ 5.6875) = 26 rows. At 16 ft long that's 416 lineal feet — 457.6 after the default 10% waste — which rounds up to 29 sixteen-foot boards. Screws are figured at 3.5 per square foot (two per board at every joist, joists 16" on center: about 700 screws per 200 sq ft), and the joist count assumes 16" on-center framing across the length, each joist spanning the width. Use 15% waste for diagonal decking or picture-frame borders.
Worked example — 16 × 12 ft deck, 5/4×6 boards
Rows = ceil(144" ÷ (5.5" + 0.1875")) = 26 Lineal = 26 × 16 ft × 1.10 waste = 457.6 ft Boards = ceil(457.6 ÷ 16 ft) = 29 Joists = ceil(192" ÷ 16") + 1 = 13 (12-ft, 16" OC) Screws ≈ 192 sq ft × 3.5 ≈ 672 Actual board widths: 5/4×6 and 2×6 = 5.5", 5/4×4 = 3.5"
Frequently Asked Questions
How many deck boards do I need for a 12×16 deck?
With standard 5/4×6 decking (5.5" actual width) and a 3/16" gap, a 16×12-ft deck needs ceil(144 ÷ 5.6875) = 26 rows of boards across its 12-ft width. That is 416 lineal feet, about 458 after 10% waste — 29 sixteen-foot boards. Switch to 3.5"-wide 5/4×4 boards or change the gap and the row count changes, so rerun the numbers with your exact spec.
What gap should I leave between deck boards?
1/8" to 1/4", with 3/16" the common target for drainage and cleaning. Wet pressure-treated boards are often butted tight because they shrink about 1/4" as they dry, while kiln-dried lumber should be gapped at install. Composite decking makers specify their own gap — usually 1/4" side-to-side — so follow the manufacturer's chart.
How many screws do I need for a deck?
Plan on roughly 3.5 screws per square foot with joists 16" on center — two screws per board at every joist crossing. That works out to about 700 screws for a 200 sq ft deck, so a 5-lb box of #10 × 2.5" deck screws (roughly 350 screws) covers about 100 sq ft.
How many joists does a deck need, and what size?
At 16" on-center spacing, joist count is the deck length in inches divided by 16, rounded up, plus one — a 16-ft-long deck framed across a 12-ft width needs 13 joists. Sizing depends on span: a 2×8 typically spans 11–12 ft at 16" centers depending on species and grade, so confirm against the DCA 6 deck span tables or your local code before buying.