Fence Calculator
Calculate how many posts and panels you need for a fence, from its total perimeter.
How we calculate it
Posts = ceil(Perimeter / Post spacing) + 1, Panels = ceil(Perimeter / Panel width).
Understanding your estimate
Fence math looks simple until you are standing at the property line with a tape measure. Come up one post short halfway through the run and you are either driving back to the yard or setting an oddly spaced post just to close the gap. Buy too many panels and they sit against the garage wall for a season. This calculator takes three numbers, your total perimeter, the spacing you want between posts, and the width of one panel, and turns them into exact quantities to buy.
A 100 ft yard, worked out
Say you are fencing a yard with a 100 ft perimeter, posts every 8 ft, and 8 ft panels, the calculator's own defaults.
- Perimeter divided by post spacing: 100 ÷ 8 = 12.5 spans.
- Round up to a whole span: 13.
- Add one more post for the run's two ends: 13 + 1 = 14 posts.
- Panels follow the same division without that extra post: 100 ÷ 8 = 12.5, rounded up to 13 panels.
Why the +1 survives even on a closed loop
The +1 in the post formula comes from straight-line fencing: a run with two loose ends needs one more post than the number of spans between them, the same reason a fence of one span needs two posts, not one. A perimeter measurement describes a closed loop instead, where the last post ties back into the first and that extra post is technically redundant. We kept the formula exactly as written anyway. Whatever the shape of the yard, an extra post costs you a hole you did not strictly need to dig. A missing one costs you a section of fence that does not close. Every rounding choice in this calculator answers to the same rule: when the math is ambiguous, it errs toward more material, never less.
Why there is no waste factor field
Our Concrete Calculator asks for a waste percentage because wet concrete spills, subgrades sit uneven, and the volume you pour rarely matches the volume you measured on paper. None of that applies here. A fence panel or a post is a whole unit bought to a fixed spec, and the spec behind this calculator does not call for a waste allowance on top of that rounding. The cushion this job needs is already built into rounding each count up to the next whole post and the next whole panel.
Posts and panels never round down
12.5 spans becomes 13, not 12, and that is not negotiable anywhere in this calculator. A fence held up by one fewer post than the run needs is not a fence with a slightly wider gap. It is a fence with a weak section, since every panel is supposed to land on a post at each end. One extra post in the truck bed costs you nothing you were not already planning to spend. One missing post costs you a trip back to the store with a half-built fence line sitting open in the yard.
What this calculator does not do: concrete for the post holes
This calculator answers exactly two questions: how many posts, how many panels. It does not touch what goes around the base of each post once it is set. If you are setting posts in concrete, run the hole diameter and depth through our Concrete Calculator using the circular shape, built for exactly that kind of footing, sonotubes and post bases, rather than for slabs. Keeping the two calculators separate means each one only asks for the numbers its own job actually needs.