Type in your deck size and get the full shopping list — boards, joists, screws or clips in the pack sizes shops actually sell, posts, concrete and the total cost. No sign-up. The working is shown under every number, so you can check it yourself.
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Estimate only — not a guarantee. Mistakes are possible, so always check the quantities with your supplier or a builder before you buy or build. See the disclaimer below.
Every figure above comes from these formulas, using your numbers. This is the same maths suppliers use — if a figure ever looks off, you can check it here line by line.
Check it yourself: a 12 × 12 ft deck with 5.5″ boards, a 1/8″ gap, straight pattern and 10% waste is a standard worked example — the answer should be 29 boards. Load those exact settings and see.
Divide your deck width by one board's width plus the gap — that gives the number of rows. Multiply by how many board lengths fit along your deck, then add waste. Example: a 12 ft wide deck with 5.5″ boards and a 1/8″ gap needs ⌈144″ ÷ 5.625″⌉ = 26 rows; one 16 ft board covers each row, and 10% waste brings it to 29 boards.
The usual industry range is 5–15%, and it depends on the pattern: straight rows waste the least, diagonal cuts waste more, and herringbone wastes the most because nearly every board is cut twice. This calculator sets 10% for straight, 15% for diagonal and 20% for herringbone — you can change it. When in doubt, round up: one spare board is cheaper than a second trip.
16″ is the standard for wood deck boards laid straight. Switch to 12″ if you're laying boards diagonally or using most composite boards — they flex more and need the support. 24″ is only for thick 2× boards on low, ground-level decks, and some local codes don't allow it. Always confirm with your local building code.
Two screws at every point where a board crosses a joist. This calculator counts your board rows × your joist count × 2 — for a typical deck that lands around 350 screws per 100 sq ft. Screws are sold in boxes (this calculator uses 350-count boxes for face screws, 90-count boxes for hidden clips), and it rounds up to whole boxes so you never run short mid-job.
This estimate spaces posts no more than 6 ft apart in both directions, one footing per post, and allows 2 × 80 lb bags of concrete per footing — a common allowance for a standard poured footing. Soil, frost depth and local code can change this a lot, so treat footings as the roughest number on the list and confirm before you dig.
Yes — through waste. The boards themselves cover the same area, but a diagonal deck cuts the end off almost every board, and herringbone cuts both ends at angles. That's why switching the pattern above raises the waste allowance and the board count, instead of pretending all patterns cost the same.
This calculator gives estimates for planning only. It is not a guarantee, and it is not professional advice. The figures are worked out automatically from standard rules of thumb and the numbers you enter. They can be wrong — because of rounding, unusual deck designs, site conditions, product differences, or an error in the calculator itself.
Always verify before you spend money or start work. Confirm all quantities, lumber sizes, spans, footing depths and fastener counts with your material supplier, a licensed builder or contractor, and your local building code or building department. Building codes differ by area and are the law where you live — this calculator does not check them.
No liability. By using this calculator you agree that the site owner accepts no responsibility or liability for any loss, cost, damage, injury, wasted material, failed inspection, or any other problem that results from using these estimates — whether the cause is an error in the calculation, the prices or figures you entered, or anything else. The final decisions about what to buy and how to build are yours, so double-check everything with a qualified professional first.
Prices are examples you can change — they are not live prices, quotes, or offers to sell anything, and the actual cost of your project will differ.