Free US quantity worksheet
Deck Calculator for Straight Surface Board Quantities
Plan surface board quantities for a rectangular deck with straight parallel rows. Enter the actual board width, gap and stock length. The model rounds stock pieces within each row and adds your chosen extra allowance without reusing offcuts between rows.
Starting figures illustrate the calculation. Replace them with verified measurements and the actual product details. Allowances are your choice, not a recommended rate.
Your quantity result
- Deck surface area (sq ft)
- 120
- Board rows, including any ripped edge row
- 22
- Stock pieces per row before allowance
- 1
- Stock boards before extra allowance
- 22
- Stock boards with extra allowance
- 25
- Purchased board length with allowance (linear ft)
- 400
Straight parallel surface rows only, no reuse of offcuts between rows. Each row rounds up to whole stock pieces before extra allowance. Gaps and dimensions must come from the actual product. No framing, spans, fasteners, stairs, railing or structural design.
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Calculate rows using actual width and gaps
For N rows, the covered width is N × board width + (N - 1) × gap. Therefore rows = round up ((deck width in inches + gap) / (board width + gap)). A final row may need ripping; the calculation counts it as a row.
Stock pieces per row = round up (deck length along the boards / stock board length). Multiply by rows for the base stock count, then apply and round up the extra stock allowance. Purchased linear feet = final stock count × stock length.
For a 12 ft by 10 ft surface, 5.5-inch faces, an entered 0.1875-inch gap and 16 ft stock, the model counts 22 rows and 22 base boards. A chosen 10% extra allowance gives 25 boards. These example dimensions and gap are not a product installation specification.
Use product dimensions and a separate construction plan
Trex lists actual face dimensions and available stock lengths by profile. Its spacing guidance varies with the product and circumstances. Use the requirements for the actual material and fastening system rather than treating an example gap as universal.
This worksheet excludes diagonal patterns, picture frames, breaker boards, borders, stairs, fascia, railings and offcut optimization. It does not size joists, beams or footings, count fasteners, choose spans or establish code approval. Row splices and supports require their own appropriate layout.
Sources and checked dates
- Trex: actual board profiles and stock lengths(2026-11-11)
- Trex: product-specific board spacing considerations(2026-11-11)