How to Estimate a Deck Job (With a Worked 12 × 16 Example)
October 29, 2026 · 4 min read
A deck estimate comes down to counting framing, decking, footings and hardware, then adding labor and markup. Here is a simple method you can reuse on every deck bid.
Step 1: Measure the deck area
Multiply width by projection. A 16 ft wide deck that sticks out 12 ft from the house is 16 × 12 = 192 sq ft.
Step 2: Count the joists
At 16 inches on center across a 16 ft width: (16 × 12 ÷ 16) + 1 = 13 joists, each 12 ft long. Add two 16 ft rim joists. Always confirm joist size and span with your local code tables.
Step 3: Count decking boards
A 5.5 in board with a 1/8 in gap covers about 5.625 in. Across 12 ft (144 in): 144 ÷ 5.625 = 25.6, so 26 rows of 16 ft boards. Add 10% waste: 26 × 1.1 = 28.6, round up to 29 boards.
Step 4: Footings, posts and beam
For a ledger-attached deck with one outer beam, plan 3 posts and 3 footings, plus a doubled 16 ft beam. Footing depth depends on your frost line and inspector.
Worked example: 12 × 16 pressure-treated deck
The prices below are example numbers only. Use your own supplier pricing.
| Item | Math | Cost |
|---|---|---|
| Decking | 29 × $45 | $1,305 |
| Joists (2×8×12) | 13 × $22 | $286 |
| Rim joists (2×8×16) | 2 × $30 | $60 |
| Beam (2×10×16, doubled) | 2 × $38 | $76 |
| Posts (6×6×8) | 3 × $45 | $135 |
| Footings (concrete + forms) | 3 × $40 | $120 |
| Hardware, fasteners, flashing | allowance | $350 |
| Materials | $2,332 | |
| Labor | 2 people × 3 days × 8 hr = 48 hr × $65 | $3,120 |
| Markup on materials | 15% × $2,332 | $349.80 |
| Total (before permit and stairs/railing) | $5,801.80 |
Don't forget
- Stairs and railings, priced per step and per linear foot
- Permit and inspection fees
- Demo and haul-away of an old deck
- Composite decking costs more per board, so redo Step 3 pricing
Send it the same day
Clients often go with the contractor who answers first. With Quote Commander you can describe the job on site and send a professional proposal the client can sign online. See more estimating guides or check pricing.
Frequently Asked Questions
At 16 inches on center, (16 × 12 ÷ 16) + 1 = 13 joists. Confirm size and span with local code.
With 5.5 in boards and a 1/8 in gap, about 26 rows, or 29 boards with 10% waste.
About 10% is a common starting point; use more for diagonal patterns.
Put the paperwork in one place.
Create proposals, collect signatures, send invoices and keep client records in Quote Commander. New job-management tools are in preview. Solo stays $29/month and Pro $79/month, with annual options.
