How to calculate decking
Deck area is divided by the coverage width of one linear foot of board. The calculator uses actual board width plus the planned gap, then adds waste and converts the total to whole boards.
Decking formula
Linear feet = deck area × 12 ÷ (board width + gap). Whole boards equal linear feet × (1 + waste) ÷ board length, rounded up.
Worked example
A 16 × 12 foot deck is 192 square feet. With 5.5-inch boards, a 1/8-inch gap, 16-foot lengths, and 10% waste, the estimate rounds to 29 boards.
Practical tips
- Use actual board width rather than the nominal lumber name.
- Plan board direction, seams, breaker boards, stairs, and picture framing separately.
- Follow the product maker's gap and joist-spacing requirements.
Assumptions and limitations
This area-based estimate assumes parallel boards across one rectangle. It excludes framing, fascia, railings, fasteners, stairs, and layout-specific offcuts.
Frequently asked questions
How much decking waste should I add?
Ten percent is a common starting point; diagonal layouts and detailed borders often require more.
Does the board gap reduce material?
Yes. The gap contributes to covered width, which this calculator includes.