About the Decking Calculator
Enter your deck size, board width, board length, and the gap between boards to get the number of surface boards to buy, plus the total lineal feet. Framing and fasteners are separate.
How it’s calculated
Board coverage = (board width + gap) ÷ 12 × board length. Boards = deck area × (1 + waste%) ÷ coverage, rounded up.
Example calculation
A 16 × 12 ft deck with 5.5 in boards, a 1/8 in gap, and 10% waste needs about 29 boards.
Frequently asked questions
Does this include framing?
No — it counts surface (decking) boards only. Joists, beams, posts, fasteners, and fascia are estimated separately based on your framing plan.
Why does the gap matter?
The gap between boards (for drainage and expansion) adds to each board's effective width, which slightly reduces how many boards you need.
This is a general material estimate for planning only. Actual quantities vary with waste, offcuts, site conditions, product coverage, and technique. Confirm measurements and coverage rates before ordering, follow local building codes, and round up — running short mid-project is costly.