Deck Materials Calculator
Work out every board, joist, beam, post, footing and screw in your deck — plus a printable cut list and the total material cost. Share the plan with a link.
Deck size & layout
Decking material & hardware
Railing, stairs & waste
How to use this calculator
1. Measure the deck, then pick the board direction
Length and width are the finished deck footprint. The board direction decides everything downstream: boards laid parallel to the length are cut to the length, and the rows stack across the width, so the width is what gets divided by the board pitch. Flip the orientation and the two swap. Joists always run at right angles to the boards.
2. Set the board pitch
Face width plus gap is the pitch — the distance from the edge of one board to the same edge of the next. Nominal sizes lie: a 5/4x6 and a 2x6 both measure 5.5 inches. With the usual 1/4 inch gap that gives a 5.75 inch pitch, so a 12 ft run needs 26 rows, not the 24 you would get by dividing by 6.
3. Frame it: joists, beams, posts, footings
Joist count comes from the spacing you choose plus one for the closing joist. Beams are placed so no joist ever spans further than the figure you enter, and posts sit under the beams at your post spacing. A ledger-attached deck drops one whole beam line — and all of its posts and footings — because the house wall carries that edge.
4. Price it and print the cut list
Every price is editable, so paste in the numbers from your own lumber yard. Open the material and cut list tab for a row-by-row order sheet with lengths and quantities, then download it as CSV or print it to carry to the counter.
Deck material FAQs
How many deck boards do I need?
Count rows first. A 5/4x6 board is 5.5 inches wide and sits with a 1/4 inch gap, so every row eats 5.75 inches. Divide the span the boards cross by that pitch and round up: a 12 ft deep deck needs ceil(144 ÷ 5.75) = 26 rows. Multiply the rows by the board run to get linear feet, add your waste percentage, then divide by the stock length you plan to buy to get the board count.
What joist spacing should I use?
16 inches on center is the standard for pressure-treated and cedar decking laid square to the joists. Most composite and PVC boards require 16 inches on center for perpendicular installs and 12 inches on center for a 45° diagonal pattern, because the board spans further between bearing points on the diagonal. 24 inches on center is only appropriate for thick 2x6 decking — check the board manufacturer's span table before you frame.
How much does a deck cost per square foot in materials?
Materials alone usually land between $15 and $30 per square foot for pressure-treated, $25 to $40 for cedar, and $35 to $60 for composite once railing and stairs are included. Railing is the line item that surprises people: it is priced per linear foot and can be a quarter of the whole bill on a small deck. This calculator prints a dollars-per-square-foot figure so you can sanity check a contractor quote — labor typically doubles the number again.
How many screws do I need per square foot of decking?
Face screwing uses two screws at every joist crossing, which works out to roughly 350 screws per 100 square feet, or about 3.5 screws per square foot. Hidden clips are counted differently: you need one clip at every board-and-joist intersection, so the count is rows multiplied by the number of joists. Buy about 10% extra either way for drops and strip-outs.
How much waste should I add to a deck order?
10% is the normal allowance for a rectangular deck with square cuts. Push it to 15% when the deck has angled corners, picture framing, or a wraparound layout, and to 20% for a 45° diagonal pattern, where every board is cut on both ends and the offcuts are rarely long enough to reuse. Framing lumber is bought as whole pieces, so this calculator applies waste to the decking only.
Does this replace a permit drawing?
No. It is a takeoff and budgeting tool. Joist, beam and footing sizes are governed by your local code and your soil, and most jurisdictions require a permit for a deck over 30 inches off the ground. Use these counts to price the job and to check a quote, then have the structure sized against the span tables your inspector works from.