Deck Calculator

Count deck boards, joists and screws for a rectangular deck surface.

%

Deck boards (16 ft)

29

  • Deck area192 ft²
  • Rows of boards26
  • Joists (running across the boards)13
  • Deck screws (2 per board per joist)676
  • Linear feet of decking416 ft

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Enter deck length (along the boards) and width.
  2. Pick board width, gap and the board length you'll buy.
  3. Pick the joist spacing.

The formula

Rows = deck width ÷ (board width + gap)

Boards = rows × boards per row × (1 + waste)

Worked example

Deck length (along the boards)16 ft
Deck width (across the boards)12 ft
Board width6 in nominal (5.5 in)
Gap between boards0.1875 in
Board length you'll buy16 ft
Joist spacing16 in o.c.
Waste10 %

Result

Deck boards (16 ft)29
Deck area192 ft²
Rows of boards26
Joists (running across the boards)13
Deck screws (2 per board per joist)676
Linear feet of decking416 ft

Tips before you order

  • Composite decking often requires 12 in joist spacing on diagonal layouts.
  • Stagger butt joints over different joists.

Questions

How many deck boards for a 12×16 deck?

With 5.5 in boards and 3/16 in gaps, about 26 rows of 16 ft boards — 29 with 10% waste.