Board and joist layout
courses = deck width ÷ (board width + gap)joists = deck length ÷ spacing + 1All quantities round up. Stock-board count also accounts for the selected board length and waste allowance.
Decking calculator
Estimate deck-board courses, stock boards, joists, and face fasteners for a simple rectangular deck.
Describe the deck surface
This model assumes boards run along the entered length and joists run across the width.
Board direction changes the takeoff
Straight boards running across a rectangular deck behave differently from diagonal fields, picture-frame borders, breaker boards, stairs, and built-in features. Calculate those components separately when they use different lengths or spacing.
- Use actual board width and the installed gap.
- Choose stock lengths around the framing and planned butt joints.
- Count clips, screws, plugs, and border fasteners using the selected system's instructions.
Verify the structure
Actual span limits and fastener schedules depend on species, grade, decking product, loads, local code, and manufacturer instructions. Use an approved plan for structural sizing.