Simple rectangular takeoff
Board rows ≈ deck width ÷ board face width (include the gap you will leave). Boards along the length depend on stock length. Joists at 16" on center are common, but composites and some spans require 12" o.c.—follow manufacturer span tables and local code.
Worked example
A 16 × 12 ft deck with 5.5" face boards needs ceil(12 ÷ (5.5/12)) ≈ 27 rows. With 12 ft boards matching the length, that is 27 deck boards, plus joists at 16" o.c. along 16 ft (13 joists) and 2 rim joists. Screw counts scale with linear feet—budget extras for leftovers and misdrives.
What this tool does not design
Stairs, multi-level decks, ledgers, beams, and footings need separate structural planning. Pair piers with the Sonotube calculator when estimating footing concrete.
Common mistakes
- Ignoring picture-frame borders that change board counts.
- Forgetting that hidden fastener systems change scrap rates.
- Spacing joists for lumber when using composite that needs tighter spacing.
| Stock length | Best when… |
|---|---|
| 12 ft | Short spans / less waste on small decks |
| 16 ft | Matches many 12×16 footprints with fewer joints |
| 20 ft | Long runs when handling allows |
Assumptions and limits
The deck material calculator results are planning estimates for rectangular or cylindrical shapes with uniform depth. Real sites have slopes, voids, and product variation. Always confirm coverage with the manufacturer label and local building practices before you buy large quantities.
Unit toggles switch input labels between US imperial and metric. Shareable URLs store your inputs in the query string for convenience, while the canonical tag stays on the clean page URL so search engines do not index every parameter combination.
Shopping checklist
- Write down the calculator outputs (volume, bags, or piece counts) and round up for waste.
- Call your supplier for density, dye lot, or delivery minimums when ordering bulk material.
- Check access for trucks, wheelbarrows, and staging space before delivery day.
- Photograph existing conditions so you can revisit dimensions if a helper measures differently.
FAQ
What board width should I enter?
Use the actual face width including the gap you will leave (for example 5.5" for 6" nominal boards with a small gap).
Is 16" joist spacing always OK?
16" o.c. is common for many boards, but composites and some spans require 12" o.c. Follow the decking manufacturer span tables.
Related guides
Sources
- AWC – Deck guide resources Used for: Deck framing practice and span-table context (not a substitute for code). Checked .
Estimates only—confirm bag yields on the product label and check local building codes before you pour or order. Not affiliated with QUIKRETE, Sakrete, Sonoco, or any manufacturer named in the sources. Found an error? Tell me.
Calculator version 1.0 · Changelog