01
Formula
Rows = ceiling of (width inches ÷ board width).
Pieces per row = ceiling of (deck length ÷ board length). Boards = ceiling of (rows × pieces per row × (1 + waste)). Joists = floor(length inches ÷ spacing) + 1.
Apply for financingDeck calculator
Deck calculator for boards and joists
This deck calculator counts deck boards and joists for a rectangular deck. It is not a complete deck cost calculator: posts, beams, footings, hardware, and railings are outside the count.
Deck boards
30boards
Deck area192 sq ft
Board rows27
Joists13
Each joist12 ft
Board and joist count only. Posts, beams, footings and fasteners need a design for the span, the species and the local code. This is not that design.
How it works
Boards run the length. Joists run the width.
Enter the deck length in the direction the boards run and the width across the boards. Joists are spaced along the length. The count is the length in inches divided by the spacing, rounded down, plus one. Each joist is as long as the width. Board rows are the width in inches divided by the coverage width of one board, rounded up. If a board is shorter than the deck, more than one piece is needed in the row. Waste applies to the board count only. A 5.5 inch coverage width is a typical 6-inch nominal board. Use the actual coverage of the product.
02
Example
A 16 by 12 foot deck, 16 inch joist spacing, 5.5 inch boards.
The area is 192 square feet. Boards that are 16 feet long need one piece per row. The width needs 27 rows. With 10% waste, order 30 boards. The joist count is 13, each 12 feet long. That is not a beam or a post schedule.
03
Tips
Spacing is a design input, not a default you must keep.
Sixteen inches on center is a common starting point, not a span rating. Species, joist size, and the decking product decide what spacing is allowed. Railings, stairs, and picture framing use extra board this page does not add.
04
Equipment
Footings are auger work.
A skid steer or an auger is separate from the board count. Dengaro finances business equipment from $15,000 to $2 million. Use the button for that request. Do not treat the board tally as a project bid.
Important questions
Know what to expect.
Why isn't this a full deck cost calculator?+
A cost needs posts, beams, footings, hardware, railing, stairs, and labor, and those depend on the design. This page stops at boards and joists so it does not pretend to price a deck.
What if my boards are 8 feet on a 16 foot deck?+
Set the board length to 8. The calculator puts two pieces in each row before waste. Joints should land on a joist. The page does not check that layout.
Does the joist count include a rim?+
The count is the joists across the length, including both ends. A rim board or beam is additional lumber. Add it from the deck width or length, outside this number.
Can I change the board width?+
Yes. Enter the coverage width in inches, the face the board actually covers, not the nominal name, if the product is narrower than its label.
Financing built into the sale