Fence Post Spacing Calculator
Calculate exact on-center post spacing and section divisions to prevent short awkward end panels on any fence length.
Fence post spacing
Enter your measurements and the result updates as you type.
Overview
Blindly spacing posts at an even 8 feet often leaves a tiny, awkward 2-foot panel at the end of a fence run. This calculator divides your total distance into equal, uniform section spans.
Equal section spacing ensures structural balance, uniform appearance, and predictable lumber purchase cuts without short, fragile end sections.
Common mistakes
- Measuring post spacing from post edge to edge rather than center-to-center, throwing off prefabricated panel installations.
- Exceeding 8 feet on center for wood privacy fences, causing 2x4 backer rails to sag in hot weather.
- Setting unequal bays that require cutting every single picket or rail to a different custom length on site.
- Ignoring gate width deductions prior to laying out post centers along the boundary string line.
Related calculators
- Fence post calculator Calculate line posts, corner posts and end posts from run length and spacing, with concrete for each post included in the take-off.
- Fence Post Length Calculator Find total post length based on fence height, local frost line depth, and drainage gravel base with recommended lumber sizes.
- Fence Section Calculator Compute full pre-built fence panels, partial end cuts, gate deductions, and total posts needed across your property line.
- Fence rail calculator Work out how many horizontal rails a fence run needs from its length, post spacing and rails per section, with the math shown.
Related reading
In-depth guides
Frequently asked questions
What is on-center post spacing?
On-center (OC) measurement is taken from the exact center point of one post to the exact center point of the adjacent post, matching standard lumber lengths.
Why should I divide my fence run into equal sections?
Equal spans eliminate narrow partial end bays, make all rail cuts identical, distribute wind resistance evenly, and look professional from the street.
What happens if posts are spaced 10 feet apart on a wood fence?
Ten-foot spans cause wood 2x4 rails to sag under picket weight, bow in high wind, and cup or twist in changing moisture conditions.
How far apart should posts be on vinyl privacy fences?
Most vinyl fence panels are manufactured for exactly 6-foot or 8-foot on-center post spacing and cannot be stretched further.
How do you space posts on an 85-foot fence run?
Rather than ten 8-foot sections and one awkward 5-foot section, divide 85 feet into 11 equal sections of 7.73 feet (7 feet, 8-3/4 inches) on center.
Do gate openings change the post spacing calculation?
Yes. Subtract the total gate opening width from the overall boundary run first, then calculate equal post spacing for the remaining fence runs.
What is the best post spacing for high-wind areas?
In open rural plains or coastal hurricane zones, reduce privacy fence post spacing to 6 feet on center and upgrade to 6x6 posts.
Does post spacing change when building on a slope?
On slopes, spacing is measured horizontally along level string lines, so the actual sloped run between posts will be slightly longer than horizontal spacing.