Math & Everyday
Fence Calculator
Posts and rails needed for a fence run, from total length and post spacing.
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CalcoTools · Fence Calculator · generated 9/1/2026, 2:28:16 PM
About the Fence Calculator
Calculates the number of posts and rails needed for a straight run of fence, from the total length and post spacing.
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How to use it
- Enter the total fence length.
- Enter the post spacing — 8ft is standard for wood/vinyl/composite, up to 10ft for chain link.
- Optionally enter rails per section.
- Read the posts, sections, and rails needed.
Formula
Sections = ceiling(total length ÷ post spacing). Posts = sections + 1. Rails = sections × rails per section.
Worked example
A 100ft fence run at 8ft post spacing with 3 rails per section: 13 sections, 14 posts, and 39 rails.
Typical post spacing by fence type
| Fence type | Typical spacing |
|---|---|
| Wood / vinyl / composite (solid) | 8 ft |
| Chain link | Up to 10 ft |
| Wire / barbed wire (open) | 10-12 ft, less on slopes |
Interpreting your result
This models one straight run of fence only — it does not account for corners (each needs its own post), gates (need dedicated, more heavily-set posts), or slopes/uneven terrain (commonly need closer spacing).
Recommendations
- • Add one post per corner beyond this calculator's straight-run count.
- • Gates need two dedicated, more heavily-set posts sized to the gate's weight.
- • Sloped or uneven terrain commonly needs closer-than-standard spacing.
Frequently asked questions
A fence needs a post at both ends of every gap between posts.
Related searches
Sources
- Family Handyman — How Far Apart Should Fence Posts Be? — accessed 2026-08-30