Deck Board Calculator

Estimate straight deck-board coverage

Enter the rectangular surface dimensions, actual board face width, planned gap, stock length, and waste allowance. The tool counts rows across the deck and converts their combined length into whole stock boards.

Board width and gap work together

A nominal 6-inch deck board may have an actual face width near 5.5 inches. The gap is open space between adjacent boards. Adding face width and gap gives the repeating coverage across the deck. Use dimensions for the exact product and fastening system instead of relying on a nominal label.

Calculation method

The deck width is converted to inches and divided by board face width plus gap. That result rounds up to a whole row. Rows multiplied by deck length give linear footage before waste. The adjusted footage is divided by stock length and rounded up to a whole-board purchase count.

Worked example

A 20-foot-long deck that is 12 feet wide uses 5.5-inch boards with a 0.125-inch gap. The 144-inch width needs 26 rows. Those rows total 520 linear feet. Adding 10 percent produces 572 feet, which requires 36 whole 16-foot boards when treated as pooled linear stock.

Plan the cut layout separately

Linear footage does not prove that a particular set of board lengths will fit the layout. Butt-joint placement, joist spacing, picture-frame borders, breaker boards, angled patterns, end trimming, and manufacturer span rules affect cuts. Sketch rows and joints before purchasing, especially when deck length exceeds available stock.

Choose waste for the job

A plain rectangle with stock lengths that fit efficiently may need little extra. Diagonal decking, borders, defects, rejected appearance boards, complex edges, and short reusable offcuts can change the allowance. Supplier return rules and color-lot consistency can also influence whether a modest reserve is useful.

Limitations and safety

This is a surface-material estimate only. It does not design beams, joists, footings, railings, stairs, fasteners, ventilation, drainage, or structural connections. It does not check building code, product instructions, loads, permits, or property boundaries. Measurements stay in this browser.