Estimate deck boards, rows, linear footage, waste, fasteners, and material cost using actual board width, gap, orientation, and purchasable board length.
For dimensioned rectangular sections, CalcRocket calculates gap-aware row count across the deck and multiplies rows by the board run length.
Waste is applied once to base linear length. Recommended linear length is divided by purchasable board length and rounded upward using the shared purchase helper.
length × width × quantityceiling((span + gap) ÷ (board width + gap))rows × run lengthbase linear length × (1 + waste % ÷ 100)ceiling(recommended linear length ÷ board length)whole-board purchased length − recommended linear lengthA 20 × 12 ft deck with 5.5 in boards and a 1/8 in gap has 26 rows when boards run along the 20 ft direction. Base length is 520 linear ft; with 10% waste, 572 ft requires 48 twelve-foot boards, purchasing 576 ft with about 4 ft surplus.
A 12 × 12 ft deck with the same board module uses the implementation's boundary-aware row formula. With boards matching the run, waste is applied to total linear length before board rounding.
For a 6 × 4 m deck using 140 mm boards and 5 mm gaps along the 6 m direction, the calculator derives 28 rows and 168 base linear meters before waste.
Use measured or manufacturer actual width, not nominal lumber naming.
The final row has no gap after it, which is why the boundary-aware row formula includes one gap in the numerator.
Compare material geometry only. Joist direction and structural design determine allowed board direction.
Known-area mode divides area by actual board width for a conservative linear-material estimate. Without deck dimensions, it cannot claim a row count or gap-aware layout.
The purchase count is a linear-length estimate. Offcuts may sometimes be reused, while whole-board row segmentation may overestimate. Actual layout, joints, patterns, and stock lengths can change quantity.
Fasteners use a user-entered per-board rate without assuming face screws or hidden clips. Optional cost supports price per board or per linear unit and excludes framing, railings, stairs, concrete, labor, delivery, and taxes.
This calculator estimates decking surface material only. It does not size or verify joists, beams, posts, footings, ledgers, spans, connections, structural loads, or code compliance.
Calculate gap-aware rows and run length, apply waste to total linear length, then divide by purchasable board length.
Multiply deck length by width and quantity.
Narrower actual boards generally require more rows.
Use actual installed board width.
Rows use the smallest whole number satisfying all board widths plus gaps between boards.
For dimensioned decks, row count is multiplied by run length.
Cuts, defects, trimming, and offcut inefficiency vary; the editable default is 10%.
Recommended linear length is divided by selected purchasable board length.
Sometimes, but reuse depends on layout and cut positions and is not guaranteed here.
Yes; span determines row count and run determines linear length.
Optionally, using your fasteners-per-board rate.
No. It is not a structural design calculator.
No. Cost is decking material only.