Decking Calculator
Plan deck surface board quantities for a rectangular layout.
Calculate your materials
Your estimate
Enter your measurements and select Calculate estimate to see the results.
Estimates are for planning only; verify product specifications and local requirements.
How this decking calculator works
This calculator estimates surface decking boards, not beams, footings, joists or fasteners. It assumes boards run along the entered deck length and courses span its width. For a reliable order, choose the actual board face width and approved gap for your product.
The calculation
Courses = round up((deck width in inches + gap) ÷ (board face width + gap)). Stock boards per course = round up(deck length ÷ board length). Total boards = round up(courses × stock boards per course × (1 + waste percentage)).
Worked example
For a 16 ft × 12 ft deck, 5.5 in boards with 1/8 in gaps need about 26 courses. Using 16 ft stock boards and 10% overage, estimate 29 surface boards.
Before buying materials
- Use the actual face width, not the nominal lumber dimension.
- Staggered seams and mixed stock lengths can change the count.
- Structural deck design and code compliance require separate planning.
Frequently asked questions
Does this include framing lumber?
No. It covers surface decking boards only.
Can I use composite boards?
Yes, provided you enter the actual face width and manufacturer-specified gap.
What about board seam staggering?
This is a simplified material estimate; a detailed cutting plan can change quantities.