Deck Calculator for a 12×12 Deck
Estimate boards and fasteners for a 12×12 ft deck.
A 12×12 ft deck (144 sq ft) is a classic entry-level DIY size — big enough for a table and grill, small enough to build in a weekend. Joists on 16 in centers, 5/4 or 2×6 boards laid perpendicular to the joists, and a matching perimeter picture-frame board give a clean, professional look.
Deck boards
35
Joists
13
Screws
280
192 ft² deck
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How does the deck calculator work?
Board count = (deck length ÷ board length) × (deck width in inches ÷ board actual width). A "5/4×6" board is really 5.5 in wide. Joists at 16 in on-center: (length in inches ÷ 16) + 1.
Which guide explains this in more depth?
- Riser-and-tread math plus 2026 material prices for a full stair build. Read the stair calculator cost breakdown guide for the full worked example.
What else do people ask about this calculator?
How many deck boards for a 12×12 deck?
12 ft boards perpendicular to joists: ~28 boards (5.5 in wide with a ⅛ in gap). Add 10% waste and picture-frame boards — call it 32 boards total.
How many joists for a 12×12 deck?
Joists 16 in on center over a 12 ft span = 10 joists plus 2 rim boards. Use 2×8 pressure-treated joists at 16 in OC.
How many deck boards for a 16×12 deck?
At 12 ft boards and 5.5 in actual width, about 27 boards plus 10% waste — order 30.
How far apart should deck joists be?
16 in on-center for standard decking; 12 in for composite or for spans over 12 ft.
Which related calculators should I use next?
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