Add waste for diagonal or picture-frame patterns.
MEASURE. ESTIMATE. BUILD.
Decking Calculator
Enter your deck size and board width to get the number of deck boards, linear footage, and screws, plus joist count at your chosen spacing.
01 / PROJECT DIMENSIONS↙
Length
Width
Waste %%
ft² per boardft²
Change any measurement to update your estimate.
02 / YOUR MATERIAL ESTIMATE
You need approximately
159 boards
covers 158.4 ft² (incl. waste)
- Area to cover
- 158.4 ft²
- Exact amount
- 158.4 boards
Field notes
Order boards at the deck's full length when you can — a 16 ft board across a 16 ft deck means no butt joints to seal and stagger. Composite usually needs joists at 12 inches on center, not the 16 you'd use for wood, so check the manufacturer before you frame. The 10% waste covers cut-offs and the occasional cupped board; picture-frame borders and diagonals push it higher.
How the decking calculator works
The math behind the tool:
boards = deck width ÷ (board width + gap)
linear ft = boards × deck length × (1 + waste%)Sources: American Wood Council (DCA 6) (residential deck joist and board span tables).
Frequently asked questions
How many deck boards do I need?
Divide the deck width by the board width plus the gap (typically 5.5 in + 0.25 in) to get boards per row, then multiply by rows and add 10% waste. A 12×16 ft deck needs roughly 33 boards of 16 ft.
How far apart should deck joists be?
Deck joists are usually spaced 16 inches on center; composite decking often requires 12-inch spacing — check the manufacturer and DCA 6 span tables.
How do you calculate stairs for a deck?
Measure the total rise from the finished ground to the top of the deck surface, divide by 7 inches and round to a whole number of risers, then divide the rise back by that count. Multiply the tread count — one fewer than the risers — by your tread depth for the total run.
Related calculators
Step-by-step guides
Embed this calculator on your site
Add this free tool to your own site. Copy the code below — it includes a link back to BuildCalculator.
<iframe src="https://buildcalculator.app/embed/decking/" width="100%" height="520" style="border:1px solid #e5e3dc;border-radius:12px" loading="lazy" title="Decking Calculator by BuildCalculator"></iframe>
<p style="font-size:12px"><a href="https://buildcalculator.app/decking/">Decking Calculator by BuildCalculator</a></p>