Easy Wood Calc

How many deck boards for a 12×12 deck?

Short answer

A 12 × 12 ft deck needs 29 boards of 14 ft decking — 26 rows of 5½ in boards plus 10% waste — and about 520 screws at two per joist, or 260 clips if you use hidden fasteners. Each row is 146 in (12 ft 2 in) with a 1 inch overhang at each end, so 12 ft boards come up short.

How to work it out

  1. (144 in + 3/16 in gap) ÷ (5-1/2 in + 3/16 in) = 25.35 → 26 rows
  2. Each row = 144 in + 2 × 1 in overhang = 146 in (12 ft 2 in)
  3. One row from each 14 ft board → 26 boards × 1.1 waste = 29 boards
  4. 144 in ÷ 16 in spacing, rounded up, + 1 = 10 joists
  5. 10 joists × 26 rows × 2 = 520 screws

A 12 ft deck sounds like a job for 12 ft boards, but let the boards overhang the frame by an inch at each end and every row is 12 ft 2 in. Buy 14s and trim, or frame the deck 2 in shorter. The screw count assumes joists every 16 in from edge to edge, 10 in all; doubled joists or blocking at the ends add a few more.

Adjust for your project

ft
Boards usually run parallel to the house, so this is usually the side along the house. Measure the frame, outside to outside.
ft
in
Often 1/8–1/4 in; follow the board maker
in
How far the boards run past the rim or fascia at each end. About 1 in is common; 0 if you trim them flush.
in
On center = middle of one joist to the middle of the next. Most decks: 16.
More options: Border · Waste allowance
A border board around all four edges, mitered at the corners. The field boards then run between the end border boards.
%
Deck boards to buy29 boards14 ft
Rows of boards
26 rows
Each row, end to end (with overhangs)
146 in (12 ft 2 in)
Linear length of decking
316 ft
Face screws (2 per joist)
520 screws
Or hidden clips (≈1 per board per joist)
260 clips
Joists the boards cross
10 joists
Deck area
144 sq ft
  • Each board leaves an offcut. If a shorter stock length still covers a row with its overhangs, buying that length may be cheaper.
  • Hidden fastener counts are a rough guide — check the clip maker’s coverage chart, which also covers start and end clips.
Check your codeCode limits vary by jurisdiction — confirm with your building department before you cut or build. (IRC R507.7)

For this job · affiliate link
Exterior deck screwsAbout 550 screws — buy them in bulk tubs rather than small boxes, rated for treated lumber (or the composite maker’s own screws).
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Rows and boards by board width (12 × 12 ft deck)

Rows and boards by board width (12 × 12 ft deck)
Board face width (actual)Rows of boardsDeck boards to buyFace screws (2 per joist)
3.5 in40 rows44 boards800 screws
5.25 in27 rows30 boards540 screws
5.5 in26 rows29 boards520 screws
7.25 in20 rows22 boards400 screws

What to know about decking a 12x12 deck

  • The last row is a sliver. Twenty-five full boards plus their gaps cover about 142 in, leaving a strip under 2 in wide for the 26th row. Rather than screw down a skinny rip, trim the first and last boards so both edges get a board about 3½ in wide, or let the outer row overhang the rim a little.
  • Twelve-foot stock only works flush. Trimmed flush with the rim (no overhang), 12 ft boards cover each row with nothing to spare. With a fascia board and a 1 in overhang each end, buy 14s and trim; the 22 in offcuts make good blocking.
  • Screws come to about 520. Ten joists × 26 rows × 2 screws. Buy coated or stainless deck screws rated for treated lumber, plus a few extra for stripped heads.
  • Check the framing first. With the beam set in from the edge, a 12 ft deep deck usually has joists spanning 10 to 11 ft — see How far can a 2x8 deck joist span before you commit to 2×8s.

If your deck is longer than it is wide, the same logic scales up in How many deck boards for a 12x16 deck.

Different size? Use the full Deck Board Calculator.

What you’ll need

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Frequently asked questions

How many deck boards for a 12x12 deck using 12 ft boards?

29 boards, but only if you trim every board flush with the frame — each row is then exactly 144 in (12 ft). With any overhang at the ends, 12 ft boards are too short; buy 14s.

How many deck boards for a 12x12 deck using 16 ft boards?

Still 29 boards — one 16 ft board per row, with an offcut of about 3 ft 10 in from each. Unless the offcuts go into steps or a bench, 14 ft boards are the better buy.

How many deck boards for a 12x12 deck using 8 ft boards?

About 44 boards with 10% waste (316 ft of decking). Every row needs a butt joint over a doubled joist or blocking, staggered from row to row.

How many hidden deck clips for a 12x12 deck?

About 260 clips — roughly one per board at each of the 10 joists, before the clip maker’s start and end clips.

Other common sizes

Sources