How Many Fence Posts Do I Need?

The short answer

For each separate straight fence run, divide run length by the chosen maximum post spacing, round the number of intervals up, and add one endpoint post. Calculate separate runs independently unless they truly share an endpoint.

Use the Fence Post Calculator

Fence post counting method

Intervals per run = round up(run length ÷ maximum spacing)
Posts per separate run = intervals + 1

Rounding intervals upward keeps the actual spacing at or below the entered maximum. The spacing value is a project input, not a universal requirement.

Worked example: one 100-foot run

A straight run is 100 feet long and the planning assumption is a maximum of 8 feet between posts.

Intervals: 100 ÷ 8 = 12.5
Round upward: 13 intervals
Endpoint posts: 13 + 1 = 14 posts
Actual even spacing if redistributed: 100 ÷ 13 ≈ 7.69 ft

Result: The run needs 14 post positions under the entered 8-foot maximum-spacing assumption. Rounding 12.5 down would create spacing greater than the chosen maximum.

Why multiple runs change the count

Two separate 50-foot runs are not always equivalent to one continuous 100-foot line. At an 8-foot maximum, each 50-foot run needs seven intervals and eight posts, for 16 posts total if they do not share endpoints.

Connected runs may share a corner or terminal post depending on the actual layout. Count physical post positions from a sketch instead of subtracting endpoints automatically.

Account for gates and openings explicitly

Gate posts: Mark the posts required at each side of a gate according to the selected gate system and project plan.
Interrupted runs: An opening can create new endpoints. Treat each resulting segment as a run unless posts are shared by design.
Corners and direction changes: Record them as physical post locations before totaling intermediate spacing posts.
Spacing basis: State whether spacing is measured center-to-center or by another documented convention.

What the arithmetic cannot specify

Post spacing depends on the fence system, materials, height, loads, gates, site conditions, and applicable requirements. This method counts positions from an assumption; it does not establish the correct spacing, post size, embedment, or structural design.

Fence post questions

Why is there one more post than interval?

A line divided into intervals has a post at both ends. Three intervals, for example, require four endpoint positions.

Should the final interval be shorter?

You can distribute posts evenly along the run after rounding the interval count upward, as long as the layout remains consistent with the project plan.