How it works
Board count = ceil((deck width + target gap)/(board width+gap)); report exact equal gap if all boards can be full width, otherwise estimate the final rip width.
Input definitions
- Deck width across boards (mm)
- Enter the value in the labeled unit.
- Board face width (mm)
- Enter the value in the labeled unit.
- Target gap between boards (mm)
- Enter the value in the labeled unit.
A worked example
- Deck width across boards (mm)
- 3000
- Board face width (mm)
- 140
- Target gap between boards (mm)
- 5
Assumptions & limits
Simple parallel-board width layout only. No joist, load, fastening, edge overhang or structural design.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Does this determine a code-compliant deck gap?
No. You choose the gap. Board material, moisture movement, fixings, support spacing and manufacturer instructions must be checked separately.
How does Deck board spacing and count work?
Board count = ceil((deck width + target gap)/(board width+gap)); report exact equal gap if all boards can be full width, otherwise estimate the final rip width.
What are the limits of Deck board spacing and count?
Simple parallel-board width layout only. No joist, load, fastening, edge overhang or structural design.