Fence Length Calculator
Perimeter Minus Gates, Plus Posts
Fence estimates go wrong in two predictable places: forgetting to subtract gate openings from the total run, and underestimating post count because post spacing doesn't divide evenly into the perimeter. Both errors compound on a materials order — too few posts means a mid-project supply run, while an unadjusted gate allowance means paying for fence panels that never get installed. This calculator handles the perimeter, the gate subtraction, and the post count together.
The Formula
Fence Length = Perimeter − (Gate Count × Gate Width)
Posts Needed = ceiling(Fence Length ÷ Post Spacing) + 1
The "+1" in the post count accounts for the fact that a fence line needs a post at both ends, not just one for every interval — a 100-foot run at 8-foot spacing needs 13 intervals worth of posts, which is 12 spacing gaps plus one extra post to close both ends.
Where This Matters
- Full-yard enclosures — a rectangular yard's fence length is straightforward, but the gate subtraction matters as soon as a driveway or side gate breaks the run.
- Material ordering — both fence panel length and post count are needed to price out a project, and getting the post count exactly right avoids buying posts that then need mid-installation adjustment of spacing.
- Post spacing changes by fence type — a wood privacy fence commonly uses 8-foot post spacing, while chain-link or ranch-rail fencing may use wider spacing, which is why post spacing is a calculator input rather than a fixed assumption.
| Yard (L × W) | Perimeter | Posts needed |
|---|---|---|
| 50 ft × 30 ft | 160 ft | 21 |
| 100 ft × 60 ft | 320 ft | 41 |
| 150 ft × 100 ft | 500 ft | 64 |
| 200 ft × 150 ft | 700 ft | 89 |
These figures assume no gates are subtracted from the perimeter; add gates in the calculator to see the adjusted fence length and post count for your actual layout.
How to Use This Calculator
- Enter the yard length and yard width in feet.
- Enter the number of gates (defaults to 0) and their gate width in feet (defaults to 3 ft).
- Enter the post spacing in feet (defaults to 8 ft, a common wood-fence spacing).
- Select Calculate for the total fence length and number of posts required.
Related Calculations
Enclosing a paved area? Pair this with the Paver Calculator, or see the Tree Spacing Calculator for a privacy hedge alternative.