Decking Board Calculator
Estimate stock boards for a rectangular deck with parallel rows and a specified gap.
How to use this calculator
- Measure the relevant dimensions and select each input’s unit. Changing units converts your entered value.
- Use the coverage, dimensions or yield for the actual product you plan to buy. The starting numbers are worked examples.
- Calculate, review the assumptions below and check the final order against the project and supplier information.
Formula
Rows = round up((deck width + gap) ÷ (board width + gap)). Pieces per row = round up(deck length ÷ stock length). Order boards = round up(rows × pieces per row × allowance factor).
Worked example
A 4 m × 3 m deck with 140 mm boards, 5 mm gaps and 2 m stock boards has 21 rows × 2 pieces = 42 boards; 10% extra rounds to 47.
Common mistakes and limitations
Simple parallel rows with stock pieces counted separately in each row; no reuse of offcuts between rows. Not an optimized cutting plan. Board gaps, joint support, joists, spans, fasteners and structure must follow product/design requirements.
Questions about decking board
Are offcuts reused?
No. Each row is allocated whole stock pieces. A detailed cutting plan can change the purchase count.
Does this choose the correct board gap?
No. Enter a product-appropriate gap from your supplier or installer, accounting for material and conditions.