Decking Calculator

With 0.25 in gaps: 12 ft (144 in) divided by 5.75 in = 26 boards, each 16 ft long (the app's Boards Needed figure is not waste-adjusted). With a 10% waste factor, order about 29 boards to have material for cuts, or check the app's Total Linear Feet and Board-Feet results, which do include the 10% waste.

Use 10% for simple rectangular decks. Add 15% for diagonal installs or decks with lots of angles and notches.

A 2x6 is 1.5 in thick (stronger, better for wider joist spacing), while 5/4x6 is 1 in thick with rounded edges. Both are 5.25-5.5 in wide when dressed.

Board-feet always use nominal dimensions: BF = nominal thickness (in) x nominal width (in) x length (ft) / 12. A 2x6 at 16 ft is 2 x 6 x 16 / 12 = 16 board-feet, or exactly 1 BF per linear foot.

1/4 in (6mm) for new pressure-treated lumber; 3/16 in for composite decking per most manufacturer specs. Green lumber shrinks as it dries so a 1/4 in gap is fine even though it may look wide at first.

2x6 boards are the standard choice. They span farther between joists (up to 24 in on-center for light use), feel more solid underfoot, and require fewer boards. 2x4 boards work well for decorative patterns or light-duty small decks but need joists no more than 16 in apart.

Pressure-treated Southern yellow pine is the most affordable option. Cedar and redwood resist decay naturally and are beautiful but cost more. Tropical hardwoods like IPE last 30-50 years but require carbide tools and pre-drilling. Composite decking avoids rot and splinters but is more expensive upfront.