Deck Calculator
Decking count for a rectangular deck. Boards run along the length you enter; the calculator works out the rows across the width (board plus gap) and how many stock-length boards each row takes. Pick the stock length that leaves the least offcut. Joists run the other way.
Order 29 boards (464 lf) — pick the stock length that leaves the least offcut; 16-footers cover a 16 ft deck in one piece.
- Deck area
- 192 ft²
- Rows @ 5.50″ + 0.125″ gap
- 26
- Boards per row (16 ft stock)
- 1
- Waste 10%
- + 3
- Boards to buy
- 29
- Linear feet of decking
- 464 lf
- Joists @ 16″ o.c. (12 ft span)
- 13
- Screws / hidden fasteners
- ≈ 6.7 lb
- Materials + delivery$14–$65 / board · Sep 2026
- $506 – $1,985
- Installed (with labor)typ. $5,538
- $3,386 – $9,665
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What will this deck job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
Common deck sizes, answered
- How Many Deck Boards for a 8×8 Deck?64 ft²
- How Many Deck Boards for a 10×10 Deck?100 ft²
- How Many Deck Boards for a 12×12 Deck?144 ft²
- How Many Deck Boards for a 12×16 Deck?192 ft²
- How Many Deck Boards for a 16×12 Deck?192 ft²
- How Many Deck Boards for a 16×16 Deck?256 ft²
- How Many Deck Boards for a 16×20 Deck?320 ft²
- How Many Deck Boards for a 20×12 Deck?240 ft²
- How Many Deck Boards for a 20×16 Deck?320 ft²
- How Many Deck Boards for a 20×20 Deck?400 ft²
- How Many Deck Boards for a 24×12 Deck?288 ft²
- How Many Deck Boards for a 24×16 Deck?384 ft²
How to calculate deck by hand
Rows = Width (in) ÷ (board width + gap) · Boards = rows × ⌈length ÷ stock⌉ × (1 + waste) · Joists = length ÷ spacing + 1
Worked example
- Rows: 12 ft × 12 = 144″ ÷ (5.5 + 0.125) = 25.6 → 26 rows.
- Boards per row: 16 ft ÷ 16 ft stock = 1 → 26 boards net.
- Waste 10%: 26 × 1.10 = 28.6 → 29 boards (464 lf).
- Joists: 16 ft ÷ 16″ = 12 + 1 = 13 at 12 ft, plus 2 rim joists · Fasteners: 192 ft² × 3.5 lb/100 ≈ 7 lb of screws.
- 5.5″ boards, ⅛″ gap
- 2.13 rows per ft of width
- Decking per 100 ft²
- ≈ 215 lf of 5.5″ boards
- Screws per 100 ft²
- ≈ 3.5 lb (350 screws)
- Joists @ 16″ o.c.
- 0.75 per ft + 1
Questions crews ask
How many deck boards do I need?
Divide the deck width in inches by the board width plus gap (5.625″ for a 2×6 with ⅛″ gap) for the number of rows, then multiply by boards per row for your stock length and add 10%. A 16 × 12 ft deck takes 26 rows of one 16-footer: 29 boards with waste.
How many linear feet of decking per square foot?
About 2.15 lf of 5.5″-wide boards per square foot of deck (2.13 without waste), or 3.3 lf of 3.5″ boards. A 200 ft² deck needs about 430 lf of 5.5″ decking plus waste.
How many joists for a deck?
Deck length in inches ÷ joist spacing + 1, plus two rim joists. A 16 ft deck at 16″ o.c. needs 13 joists spanning the 12 ft width (2×10 for that span in most codes), plus rims. Composite decking often requires 12″ spacing — check the brand.
How many screws for a deck?
Two per board per joist: about 350 screws (3.5 lb of 2½″ deck screws) per 100 ft² at 16″ centres. Hidden-fastener clips run about 90 per 100 ft² of grooved composite. Buy 10% extra; they get dropped.
What gap should I leave between deck boards?
⅛″ for kiln-dried or composite boards, butted tight for wet pressure-treated lumber (it shrinks to about ⅛″ as it dries), 3/16″ for most composites per manufacturer instructions. Use a 16d nail or a gap tool as a spacer.