Cost to Build a Deck Calculator

How to use the Deck Cost Calculator

1. Enter the “Deck length (boards run along it)” and “Deck width (joists run along it)”, and choose ft, in or m. A dimension under 2 ft or over 60 ft triggers a warning. You can also click a preset: 10 × 10, 12 × 12, 16 × 12 or 20 × 16 ft.
2. Type your “Price per board” and your “Price per joist (one piece)”.
3. Type the “Labor, total” and the “Permit, total”. A blank field counts as zero.
4. Open More options for the rest. If your deck has posts, enter the “Number of posts” and the “Price per post”.
5. Enter “Fasteners, total” for screws, nails or hardware you plan to buy.
6. Enter “Other materials, total” for anything else you will pay for, such as footings, ledger flashing, railing, stairs, stain or demolition. These are not counted unless you add them here.
7. Also in More options, set the “Board” type, “Board length you can buy”, “Joist spacing, on center”, “Gap between boards (in)”, “Waste allowance (%)” and “Sales tax on materials (%)”. The default waste is 5.
8. Read “Boards to buy (with waste)”, “Joists to buy” and “Deck area”. Then check “Your total” and “Your total per ft² of deck”.

Presets set the deck size and board length, so you still need to type your own prices. Results are calculated from your inputs, so check them against current local prices before you buy.

How does a deck cost estimator add up the total cost to build a deck?

A deck cost estimator adds your materials, sales tax, labor and permit into one total. Materials are the boards, joists, posts, fasteners and other materials, each priced by you and added together.

Materials = boards x board price + joists x joist price + posts x post price + fasteners + other materials. Sales tax is applied to the materials only, not to labor or the permit. Total = materials + tax + labor + permit.

Your total per ft² is the total divided by the deck area. Area is length times width, so the figure comes only from the prices you typed. For example, with 28 boards at 10, 13 joists at 10, 6 posts at 10 and fasteners of 100, materials come to 570. Tax at 5 % is 28.50. With labor of 1,000 and a permit of 100, the total is 1,698.50. Divided by 192 ft², that is 8.85 per ft².

How many boards and joists does a deck need?

The tool sets boards to run along the deck length and joists to run across the width. It works out the number of board rows, then the number of boards by length, and adds waste.

Rows = ceil((width + gap) / (board width + gap)). Boards by length = ceil(rows x length / board length). The board count is then increased by the waste percentage, which defaults to 5 %. The board width depends on the board type. Standard 5/4 x 6 and 2 x 6 wood boards are 5.5 in wide, and 2 x 4 wood boards are 3.5 in wide. Composite widths are 5.36, 5.4 or 5.5 in, and sizes vary by maker, so check your product’s width. You can also type a width. The default gap is 1/8 in.

Joists = ceil(length / spacing) + 1. Spacing can be 12, 16, 19.2 or 24 in. The extra piece covers the far end of the deck.

Take a 16 x 12 ft deck with 5/4 x 6 boards in 16 ft lengths. It needs 26 rows, which is 26 boards by length. With 5 % waste that becomes 28 boards. It also needs 13 joists and has an area of 192 ft². A 12 x 10 ft deck with 2 x 6 boards in 12 ft lengths needs 24 boards and 10 joists. At 10 each, its materials come to 340.

Deck replacement cost works the same way. Enter the prices for new boards, joists and posts, plus your labor and permit. Demolition and disposal are not counted unless you add them to “other materials total”.

Sources (checked 15 October 2026): nist.gov · web-media.awc.org · trex.com · timbertech.com · moistureshield.com

Worked examples

Calculated by the tool above; open it with the same values to see each step.

Frequently asked questions

How much does a deck cost?

The tool cannot give one answer, because it holds no prices. Type in your own board, joist, post, labor and permit costs, and it will total them for your deck size.

What is the labor cost to build a deck per square foot?

The tool does not state a labor rate. To find it, divide your labor total by the deck area. For example, labor of 1,000 on a 192 ft² deck is about 5.21 per ft².

Is this the deck replacement cost for my existing deck?

It estimates the cost of the new materials and work you enter. It does not measure your current deck, so enter the size of the replacement deck.

Why does my total not include footings, railing or stairs?

These are not counted by default. Add their cost to “Other materials, total” in More options, so they appear in your materials and total.

Will the tool show a total if I enter no prices?

No. It shows the board count, joist count and area, and a note asks for prices. Money rows are left out until you type a price.

Is the result a quote?

No. It is a calculation from your inputs. Check local permit rules and current prices before you buy or hire.

Related tools

• Deck Board Calculator: use it to focus on board counts, waste and cut lengths before you price materials.
• Deck Board Dimensions: use it to compare board widths and thicknesses when you choose a board type.
• Deck Joist Spacing Chart: use it to compare joist spacing options before you set the spacing here.
• Deck Stain Calculator: use it to estimate how much stain your deck area may need.
• Stair Calculator: use it when your deck includes steps and you need stair dimensions.
• Stair Stringer Calculator: use it to work out stringer sizing for deck stairs.
• Deck Footing Calculator: Work out the footings under the deck.