Fence Post Spacing Calculator

How to calculate posts and equal spacing

1. Enter the run length from the centre of the first end post to the centre of the last. Choose the matching unit. Outside-edge measurements and clear openings are not the same length.
2. Enter the maximum centre-to-centre spacing chosen for your plan. Its unit is independent of the run unit. The calculator does not choose a suitable maximum or check a fence design.
3. Read total posts, equal intervals and spacing. Both end posts count toward the total. Use Same as run or choose another spacing unit; open Calculation details for the exact run-divided-by-intervals expression.

Why the count includes one more post

The number of intervals is run length divided by maximum spacing, rounded up to a whole interval. Total posts equals intervals plus one because an open straight run has a post at both ends.

Dividing the run equally across those intervals gives spacing no greater than the entered maximum. The maximum is a limit, not an exact fixed panel width or a preferred gap. No post width is subtracted.

The displayed spacing is rounded down to at most three decimal places in its selected unit. Very small positive spacing is shown as less than 0.001 unit, never zero. Counts use the original entered measurements, not the rounded spacing.

Exact spacing is the original run divided by the interval count. Repeatedly stepping out the rounded display value can move the last position away from the entered endpoint. This page is a layout-count aid, not a detailed setting-out or construction plan.

Worked straight-run examples

For a 100 ft run and an 8 ft maximum, 100 ÷ 8 is 12.5. Round up to 13 intervals, giving 14 total posts. Equal spacing is 100 ÷ 13 ft, displayed as about 7.692 ft after downward display rounding.

For a 96 ft run and the same chosen 8 ft maximum, there are 12 intervals and 13 total posts. The exact equal spacing is 8 ft. These maximum values are arithmetic examples, not installation recommendations.

A 30 m run with a chosen 2.4 m maximum needs 13 intervals and 14 total posts. Exact spacing is 30 ÷ 13 m; the displayed spacing is about 2.307 m. If the maximum is at least the run length, the result is one interval and two posts.

One open run, not a complete fence design

The tool counts one straight run between endpoint centres. Gates, corners, closed loops, shared endpoints and fixed existing intermediate posts are not modelled. Do not blindly sum runs and count a shared post twice. A total post count is not automatically a new-post shopping quantity.

It does not check panel or rail fit, post widths, height, loads, ground conditions, foundations, property boundaries or code and structural requirements. A maximum entered here is not a recommendation or a guarantee that a fence will be suitable.

Browser-side calculation

The calculator performs arithmetic in your browser and does not intentionally upload or save these inputs. Copy result uses the clipboard only when requested. Normal site services and consent settings remain separate.