Quick answer: For a simple 100 ft straight run with 8 ft spacing, the basic estimate is ceil(100 ÷ 8) + 1 = 14 posts before gate/corner adjustments.
Simple straight-run formula
Posts ≈ ceil(total length ÷ target spacing) + 1. This works as a planning check for one straight run.
Where the simple formula changes
Gates, corners, ends, changes in grade and local layout requirements can all change the final post count and post type.
Plan before buying
- Mark every corner and gate.
- Check the actual panel or rail span.
- Confirm post size, depth and footing approach.