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Deck lumber takeoff calculator
Calculate joist count, board feet of decking, and total lumber cost for a residential deck build.
Total lumber + hardware cost
Show the work
- Joists needed13
- Decking boards needed (8 ft)61
- Decking linear feet (with waste)484
- Decking cost$2,056
- Joist cost$507
Deck takeoff — just enough math to not over-buy
A deck takeoff is grade-school geometry that contractors charge $200 to do. Two pieces of lumber, one waste factor.
The two structural lines
- Joists — typically 2×8, 2×10, or 2×12 PT, spaced 16 in or 12 in OC depending on decking material and span. Joist count = ceiling(deck length in inches / spacing) + 1, each cut to deck width.
- Decking — boards run perpendicular to joists. Number of rows = deck width × 12 / actual board width.
Waste factor
10-15% on straight runs. 20% on diagonals or herringbone patterns. The waste covers crown-removal cuts, end trim, and miscuts. If your contractor adds 25%+ on a basic rectangular deck, push back.
What this skips on purpose
- Beams, posts, and footings (varies wildly by load, span, and frost depth)
- Stairs (separate calc — rise, run, stringer count)
- Railings (post + baluster + rail count)
- Ledger flashing and lag bolts (~$80-120 in hardware)
This is a decking + joist takeoff, which is the lumber that's hardest to estimate by eye. Posts/beams/stairs you can shop separately because the unit cost is well-known and the quantities are small.
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