How the post count works
A straight run divides its length by the post spacing, rounds up to whole intervals, then adds one post to close the far end — a 100-foot fence on 8-foot spacing needs thirteen intervals and therefore fourteen posts. Every gate adds one more post because a gate needs a hinge side and a latch side. Corners and direction changes each want a braced post too, so L-shaped runs cost more posts than the straight-line math suggests.
Two rails or three?
Two rails carry most privacy and wood picket fences comfortably on 6–8 foot spacing. Three rails earn their keep on taller fences, wide post spacing, stock panels, or anywhere animals (or large dogs) lean on the fence — the middle rail stops boards from bowing between posts. Rail length multiplies the full run, so three rails on a 100-foot fence means 300 linear feet of material to buy.
Frequently Asked Questions
What post spacing should I use?
Six to eight feet is standard for wood and vinyl; check your fence panel width first, because panels that span post to post lock you into their length. Windy, exposed sites often tighten spacing to six feet.
Do gates change the rail length?
A gate replaces a span of rail rather than extending the fence, so this calculator keeps rail length at the full run — you will buy slightly more rail than strictly needed, which covers the frame lumber gates consume anyway.
Are corner and end posts included?
The two ends of the run are included by the plus-one rule. Each corner or turn adds one more post that the straight-line count cannot see — add them mentally for L- or U-shaped layouts.