How to calculate fence
Posts = ⌈Length ÷ Spacing⌉ + 1 · Pickets = ⌈Length × 12 ÷ (width + gap)⌉
Worked example. Fence posts: 14 posts.
Example inputs — Fence length: 100 ft; Post spacing: 8 ft; Rails per section: 3; Picket width: 5.5 in; Gap between pickets: 0 in. Starting values are illustrative.
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
A straight fence needs one more post than it has sections. Rails run between each pair of posts, and pickets cover the length based on their width plus any gap.
Assumptions & limitations
- Results are rounded for display.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
What about corners and gates?
Add one post per corner and two per gate, and subtract the gate width from the length.