Deck Calculator to estimate deck area, decking board quantity, waste allowance, material cost, and preliminary project total.
Home & Construction Calculators
Plan deck boards from deck length, deck width, board width, waste allowance, and prices.
Use actual board coverage, include gaps and edge cuts, and confirm joist layout, fasteners, stairs, railings, drainage, and local code separately.
About the Deck Calculator
This deck calculator estimates surface area, decking board coverage, purchase quantity, waste, material cost, and preliminary project total. It is useful for early DIY and contractor planning.
Formula and assumptions
Deck area = length × width. Board coverage length is converted to inches, then deck area is divided by board coverage. Waste is applied before the purchase quantity is rounded up.
Worked example
A 20-ft by 12-ft deck has 240 square feet. With 6-in board coverage and 10% waste, the estimate is 528 linear feet of decking, or 27 boards when using 20-ft boards. Confirm the actual board length and coverage with the supplier.
Measurement checklist
- Measure each deck section separately.
- Account for angles, stairs, borders, and picture framing.
- Use actual board coverage including gaps.
- Confirm board length and supplier availability.
Manual calculation steps
- Multiply length by width for area.
- Convert deck area to square inches.
- Divide by board coverage width.
- Apply waste and round up.
- Add material, labor, delivery, and extras.
Frequently asked questions
Does this include framing?
No. It estimates decking surface materials and entered extras. Joists, beams, posts, footings, stairs, railings, and hardware need separate estimates.
Why add waste?
Waste covers cuts, defects, offcuts, layout changes, damaged boards, and difficult corners.
Can this replace a structural estimate?
No. Confirm the deck design, ledger, footing, connections, and guards with applicable requirements and a qualified professional.
Common mistakes
- Using nominal board width instead of coverage width.
- Forgetting gaps and border boards.
- Ignoring stairs and angled sections.
- Rounding before waste is applied.