How to use this calculator
- Enter the rectangular deck length in the board direction and the width across the rows.
- Enter actual board face width, clear gap, and selected stock length.
- Choose a waste allowance.
- Calculate rows, linear length, and whole stock boards.
How the calculation works
Board width plus gap determines the number of rows across the deck width. Row count is rounded upward. Rows multiplied by deck length give linear board length; waste is added before dividing by stock length.
Formula
Rows = ceil(deck width ÷ (board width + gap)) Linear board length = rows × deck length Purchase boards = ceil(linear length × (1 + waste %) ÷ stock length)
Worked example
A 12 ft by 10 ft deck with a 5.5 in board and 0.25 in gap needs 21 rows. Those rows total 252 linear feet; 10% waste and 12 ft stock boards require 24 boards.
Project considerations
- Enter actual board face width and the selected stock length.
- The calculator assumes boards run along the entered deck length and does not optimize staggered cuts.
- Joist layout, spans, structure, fastening pattern, railings, stairs, and code requirements are not calculated.
Frequently asked questions
Which direction do boards run?
Boards run along the entered deck length; the entered width is used to count rows.
Does the result optimize offcuts?
No. It converts total adjusted linear length to stock boards without a cut-layout optimizer.