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 to whole boards.
length × width × quantityceiling((span + gap) ÷ (board width + gap))rows × run lengthbase linear length × (1 + waste percentage ÷ 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 using 5.5 in boards, a 1/8 in gap, and 12 ft purchasable boards has 26 rows. Base length is 312 linear ft; with 10% waste, 343.2 ft is 28.6 exact boards, so buy 29, purchasing 348 ft with 4.8 ft surplus.
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 the selected product's actual installed width. The initial 5.5 in value is an editable example, not a universal board dimension.
The editable 1/8 in starting gap is a project assumption, not an installation requirement. The final row has no gap after it, which is why the boundary-aware formula includes one gap in the numerator.
The initial 12 ft board length and 10% waste are editable planning values. Stock lengths are product-dependent; cuts, layout, defects, and offcut reuse are project-dependent.
Compare material geometry only. Joist direction and structural design determine permitted 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, hidden clips, or a fastening schedule. 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, fastening, 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 the selected product's actual installed board width.
Rows use the smallest whole number satisfying all board widths plus gaps between boards. Enter a gap appropriate to the product and project.
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 the 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, but the calculator does not approve a structural board direction.
Optionally, using your editable fasteners-per-board rate.
No. It is not a structural design calculator.
No. Cost is decking material only.
AWC's deck guide treats framing members, spans, connections, loads, and code provisions as structural design matters beyond this surface-material estimator.