Deck build calculator
Footings, posts, beam, joists, decking, railing and stairs for a deck on a ledger, from its size — at the joist and post spacing you choose.
An estimate of the materials a job takes, worked out in your browser: check it against the job, and against your local code where it matters. Nothing you type leaves this page.
Put in the job's numbers and choices, and the list below follows them.
What it takes
Worked out for Length along the house 16 ft, Depth out from the house 12 ft, Railing 40 ft, Stair steps 4 each, Joist spacing: 16 in, Post spacing along the beam: 8 ft, Decking: Pressure-treated.
Footings and posts
- Concrete, 80 lb bag 9 bag Posts 3 each × 3: 9 bag. About three bags a footing; your frost line sets the depth — check local code.
- 6x6 pressure-treated post, 8 ft 3 each Posts 3 each: 3 each.
- Post base, 6x6 3 each Posts 3 each: 3 each.
Framing
- 2x10 pressure-treated, 16 ft 2 each ceil(Length along the house 16 ft ÷ 16) × 2: 2 each. A doubled beam.
- 2x8 pressure-treated joist 13 each Joists 13 each: 13 each. Cut to the deck's depth. The joist size and spacing are yours to choose: nothing here works out a span.
- 2x8 pressure-treated, 16 ft 4 each (Length along the house 16 ft × 2) + (Depth out from the house 12 ft × 2) at 16 a piece: 3.5 each; plus 10% waste: 3.85; rounded up to whole each: 4.
- Joist hanger, 2x8 13 each Joists 13 each: 13 each.
- Joist hanger nails, 5 lb 1 box Joists 13 each, one per 20: 0.65 box; rounded up to whole box: 1.
- Ledger lag screw, 1/2 x 4 in 24 each ceil((Length along the house 16 ft × 12) ÷ 16) × 2: 24 each.
- Ledger flashing, 10 ft 2 each Length along the house 16 ft at 10 a piece: 1.6 each; rounded up to whole each: 2.
Decking
- Pressure-treated deck board, 16 ft 29 each Deck area 192 sq ft ÷ 7.5: 25.6 each; plus 10% waste: 28.16; rounded up to whole each: 29. A 5-1/2 in board with its gap covers 7.5 sq ft in 16 ft.
- Deck screws, 5 lb 2 box Deck area 192 sq ft, one per 100: 1.92 box; rounded up to whole box: 2.
Left out: Hidden deck fasteners, 90 ct (only when Decking is Composite).
Railing and stairs
- Railing section, 6 ft 7 each Railing 40 ft at 6 a piece: 6.67 each; rounded up to whole each: 7.
- Railing post, 4x4 8 each ceil(Railing 40 ft ÷ 6) + 1: 8 each.
- Stair stringer 3 each min(Stair steps 4 each, 1) × 3: 3 each.
- Stair tread board, 6 ft 8 each Stair steps 4 each × 2: 8 each.
Labor
- Deck building 192 sq ft Deck area 192 sq ft: 192 sq ft.
- Railing installation 40 ft Railing 40 ft: 40 ft.
What it leaves out
- Permits and inspection fees
- Engineering or span tables
- Removing an old deck
The same calculator in SMG Tools
In SMG Tools this calculator fills its numbers from the client's site measurements, prices every line from your own Price Book, checks the margin against your target, and carries the lines onto the proposal, the job's plan and the purchase order. It is one of the ready-made calculators SMG Tools sets up for decks and fences, and calculators are on every plan.