The decking calculator turns deck length and width plus your board choice into a deck-surface shopping list. It returns a board count with waste, the linear decking footage behind that count, and the fastener count for whichever method you pick: face screws or hidden clips. Add a price per board and it estimates material cost. If your deck is not a clean rectangle, enter the surface area directly and skip the length-times-width step. The list covers the walking surface only: boards and the hardware that holds them down, not the frame underneath.
Turn the decking result into a buying list
Use the result as a material takeoff for the deck surface. The checks that matter are actual board width, waste, fastener method, and whether your footprint is simple enough for length times width.
Buy the rounded board count, not the exact coverage number. The calculator adds waste and rounds up because boards are purchased as whole pieces.
Face screws and hidden clips are different orders. Pick the fastening method first, then use the active fastener count and pack rounding shown in the details.
Keep 10% for a straightforward rectangular layout. Move toward 15% or more for diagonal boards, extra cutoffs, damaged stock, or a layout that has several short returns.
This is a deck-surface calculator. It covers boards, decking length, screws or clips, and optional material cost; it does not size joists, beams, posts, stairs, railings, permits, or labor.
Example: 20 ft by 12 ft deck with 5/4×6 boards
- A 20 by 12 deck has 240 sq ft of surface area.
- With 5/4×6 using a 5.5 actual face width, a 1/8 gap, 16 stock, and 10% waste, the calculator counts 26 rows, 2 per row, and 58 to buy.
- That is 928 linear feet of decking.
- If the deck is face-screwed over 16 on-center joists, the fastener estimate is 1,584 screws after the built-in hardware overage.
Use the result as a shopping list
Start with the board count and linear decking footage, then check the detail rows before ordering. If the run is longer than the board length, the calculator will show more than one board per row, which means you need enough stock to cover butt joints over framing. If you entered a price per board or fastener pack, treat the cost as a material comparison number, not a contractor quote.
What Advanced options change
Waste changes the final buy count after the base coverage math. Gap changes the coverage width, so it can add or remove full rows across the deck. Joist spacing does not calculate the frame; it only estimates how many fastener points each board crosses. Layout angle raises the board-count allowance for diagonal cuts. Area override is for L-shaped or notched decks where a single length and width would exaggerate the surface area. Pricing fields only affect cost lines; they do not change quantities.
Screws versus hidden clips
Use face screws when the boards are attached through the top face. The calculator counts two screws at each joist crossing and includes a small hardware overage. Use hidden clips when the board system fastens through grooved edges. The calculator separates starter clips at the deck ends from interior clips, then rounds the active fasteners to whole packs when a pack size is entered.
When another calculator is the better fit
Use the Deck Board Spacing Calculator when the question is exact gap layout and balanced edge margins rather than total buy quantity. Use the Lumber Calculator when the supplier quotes unrelated lumber by , lineal foot, or piece count. Use a structural framing resource for joists, beams, posts, stairs, and railings; those are outside this page's deck-surface scope.
Frequently asked questions
How many deck boards do I need?
Enter the deck length and width, the board's actual face width, and the gap between boards. The calculator divides the deck area by each board's coverage, adds your waste percentage, and rounds up to whole boards. That rounded number is the count to buy, and the page also shows the linear decking footage behind it.
Does it work for composite decking as well as wood?
Yes. The board-count math is the same for composite and wood because it depends on face width, gap, and deck area. Composite often needs a manufacturer-specified gap for heat expansion, so enter that spacing and the price per board for the product you plan to buy.
How many screws or hidden clips will I need?
Pick the fastener method first. For face screws, the calculator counts two screws per joist crossing on every board. For hidden clips, it counts one clip per interior crossing plus starter clips at both ends of each row, then rounds the hardware up to whole packs in the details.
Does this calculate joists, stairs, or railings too?
No. This is a deck-surface takeoff: boards, linear decking footage, the fasteners that hold the boards down, and optional material cost. Joists, beams, posts, stairs, railings, permits, and labor need separate structural design or a separate takeoff.
How do I use it for an L-shaped or irregular deck?
Split the footprint into simple rectangles, multiply each rectangle's length by width, and add the areas into one square-foot total. Type that total into the area override instead of forcing one length and width. The board count, waste, and fastener math then run from your supplied area.