Deck Calculator
Deck boards, joists and screws for a deckRuns in your browser
26 rows of boards, 416 linear ft. Joists, beams and posts must be sized for your span and local code; this only counts them.
Rough material cost
$1,214Rough 2026 US prices for pressure-treated lumber; composite boards cost 2–3× more. No beams, posts, footings, hardware or railings.
Material estimates only. Round up, buy a little extra, and check with your supplier. Structural work (footings, framing, roofs) must follow local building codes; consult a licensed contractor where required.
How it works
Formulas
Rows = width (in) ÷ (board width + gap)Boards = rows × deck length × (1 + waste %) ÷ board lengthJoists = deck length (in) ÷ spacing + 1Worked example
Input: 16 × 12 ft deck, 5.5 in boards, 1/8 in gap, 16 ft boards, 16 in joists, 10% waste.
- 144 ÷ 5.625 = 25.6 → 26 rows.
- 26 × 16 = 416 linear ft × 1.1 ÷ 16 = 28.6 → 29 boards.
- 192 ÷ 16 + 1 = 13 joists.
Result: 29 boards, 13 joists, about 676 screws.
Limits
- Does not size joists, beams, posts or footings; spans depend on lumber grade and local code.
How to use
- 1Enter the deck length (the direction the boards run) and width.
- 2Set the board face width and gap.
- 3Choose the board length and joist spacing.
- 4Read boards, joists and screws.
FAQ
How many deck boards do I need for a 16 × 12 deck?
With 5.5 in boards and 1/8 in gaps running the 16 ft way, 26 rows of 16 ft boards; with 10% waste, 29 boards.
What joist spacing should I use?
16 in on center is standard for wood decking laid square to the joists. Composite boards and diagonal layouts often need 12 in; always follow the board maker's span rating and local code.
Can I use metric units?
Yes. Switch to Metric and enter meters and centimeters; results show cubic meters, square meters or tonnes alongside US units.