Decking Calculator
See how much decking your project needs — total linear feet and square feet, plus the number of boards by stock length — from your deck size and board width.
Free · no sign-up ·
You need · incl. +10% waste
- Deck area
- 192 ft²
- Exact decking
- 416 lin ft
- Joists
- 13
- Joist material
- 156 lin ft
Boards to buy by stock length
Board counts include a 10% waste allowance. Linear feet is what lumberyards price from; the buy-list shows how many boards at each stock length.
The formula & specs
Square feet = length × width. Decking linear feet = (deck width ÷ board coverage) × length, where coverage = board width + gap. Boards = linear feet ÷ stock length, rounded up, plus waste.
| Board face widths (actual) | 5.5" · 5.25" · 3.5" |
| Board gaps | 1/8" · 3/16" · 1/4" |
| Joist spacing (on-center) | 12" · 16" · 24" |
| Board stock lengths | 8 ft · 10 ft · 12 ft · 16 ft · 20 ft |
Nominal board sizes differ from actual: a “6-inch” board is 5.5" wide. The calculator uses actual widths so the row count matches your real material.
How to estimate decking materials
Decking is bought by the linear foot, not the square foot — but you plan the deck in square feet, so you need both. The square footage is just length × width. To get linear feet, divide the deck width by how much each board covers (its face width plus the gap) and multiply by the deck length. As a rule of thumb, a 5.5-inch board at a 1/8-inch gap takes roughly 2.1–2.2 linear feet of decking per square foot of deck.
Coverage depends on the board, and so does the price. Wider boards cover more per linear foot, so a deck in 5.5-inch boards needs fewer pieces than the same deck in 3.5-inch boards. Material drives the budget far more than the framing — composite and hardwood cost several times what pressure-treated does per square foot. Enter your price per board in the calculator to turn the linear-foot count into a material cost.
Order by the board, allowing for waste. Convert your linear feet to a board count at the stock length your supplier carries — the calculator shows all the common lengths so you can compare. Add about 10% for cuts and culls, and 15% for a diagonal or herringbone pattern, which wastes more at the angled cuts. For composite, order it all at once: dye lots vary and lead times can run weeks.
Frequently asked questions
How much decking do I need?+
Measure your deck length and width, and the calculator returns both the square footage and the linear feet of decking — plus a board count at each common stock length. Enter the board width and gap so the coverage matches your real material.
What is the difference between linear feet and square feet of decking?+
Square feet measures the deck surface (length × width). Linear feet measures the total length of board you buy, because decking is priced by the running foot. You convert between them using the board’s coverage — its width plus the gap.
How many linear feet of decking per square foot?+
About 2.1–2.2 linear feet of decking per square foot of deck when using 5.5-inch boards with a 1/8-inch gap. Narrower boards need more linear feet per square foot; wider boards need fewer. The calculator computes it exactly from your board width.
How much decking for a 200 square foot deck?+
Roughly 430 linear feet of 5.5-inch decking for 200 square feet before waste — about 27 boards at 16-foot lengths with a 10% allowance. Enter your actual dimensions and board size above for an exact figure.
How much does decking cost?+
Decking cost is mostly the material: pressure-treated is the cheapest per square foot, composite several times more, and hardwood more again. Put your price per board into the calculator to turn the linear-foot count into a material total — framing, fasteners, and labor are extra.
How much decking for a diagonal or herringbone pattern?+
Add about 15% extra for a 45-degree diagonal layout, and more for herringbone, because the angled end cuts waste material and you also need tighter joist spacing. Toggle the diagonal option above and the calculator adds the allowance.
What size are decking boards?+
The common decking board is nominally 6 inches wide — 5.5 inches actual — in lengths from 8 to 20 feet. Composite is usually 5.25–5.5 inches. The calculator uses actual widths so the coverage and board count are right.
Do composite and wood decking cover the same area?+
Yes, at the same board width the coverage and the linear feet are identical — the difference is cost, weight, and the recommended gap. Composite often comes only in certain lengths, so check the buy-list against what your supplier stocks.
How do I convert square feet to decking boards?+
Divide the deck area by the area one board covers (board length × actual width), or let the calculator do it: enter the deck size and it returns linear feet and a board count at each stock length, including waste.
Is this decking calculator free?+
Yes — it is free, needs no sign-up, and runs entirely in your browser, so nothing you enter is stored or sent anywhere.