Fence calculator
Posts, rails, and pickets for a wood fence line — enter the total length and your spacing to get exact counts.
Fence line details
How this is calculated
The fence line is divided into sections by post spacing: sections = fence length ÷ post spacing, rounded up. Posts are one more than the number of sections, since a post sits at both ends of every section — plus one extra post per gate for the doubled post a gate hinge needs. Rails are counted as one board per section per row, so a 3-rail privacy fence uses three times as many rail boards as sections. Pickets are based on how much horizontal space each one takes including its gap: (fence length in inches) ÷ (picket width + gap), with a 5% margin added for cuts and the occasional split board.
How many posts for 120 ft of fence?
At 8 ft spacing with one gate, that's about 17 posts — 15 sections plus one end post plus one extra for the gate.
How deep should fence post holes be?
A common rule of thumb is one-third of the post's above-ground height, with a minimum of 24 inches — deeper in regions with frost heave. Check your local code, since frost line depth varies a lot by climate.
Should gate posts be different from line posts?
Yes — gate posts carry more load and torque from the swinging gate, so they're usually set in a larger hole with more concrete, and sometimes a heavier post (like 6×6 instead of 4×4).
Once you know how much to order
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Pressure-treated fence post, 4×4
Standard line post for a residential wood fence.
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