Deck Calculator
Estimate deck area and a planning count of deck boards.
Project inputs
Enter your measurements. Results update automatically.
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See estimating toolsEstimate deck area and deck boards
This calculator first finds deck area from length and width. For board count, it uses the board length, actual face width, gap and waste allowance you enter to estimate how much area each board covers.
Deck area
Length × width = deck square footage. The waste allowance is applied to that planning area before estimating boards.
Board coverage
Board coverage is based on board length multiplied by the combined face width and gap, converted from inches to feet. The final board count is rounded up.
Board layout matters
Picture framing, diagonal layouts, stairs, breaker boards, cut patterns and board direction can increase material needs. Use actual board dimensions rather than nominal size whenever possible.
Common deck calculator questions
Why use actual board width?
Nominal lumber sizes can differ from the actual finished dimensions, and composite products vary by manufacturer.
Does the calculator include framing?
No. It estimates deck surface area and planning board count, not joists, beams, posts, fasteners or footings.
Should I add waste?
Use a waste allowance that reflects the layout, cuts and material you plan to install.