Rectangle Fence Perimeter Calculator

A rectangular enclosure requires 4 corner posts, plus line posts along each of the four sides spaced every 6 to 8 feet on center, plus additional gate posts for any gate openings. For each side, the number of line posts equals (Side Length ÷ Post Spacing) minus 1. Adding 4 corner posts and 2 posts per gate opening yields the total post requirement.

Standard wood privacy fences use 8-foot post spacing to match standard 8-foot (96-inch) 2x4 horizontal backer rails. In high-wind coastal areas, regions with heavy snow drifts, or when building tall 8-foot privacy fences, 6-foot spacing is strongly recommended to prevent rail sag and provide 25% greater resistance to horizontal wind loads.

As a general building standard, 4x4 fence posts set in an 8-inch to 10-inch diameter hole dug 24 to 36 inches deep (below the regional frost line) require approximately 1.5 to 2 50-pound bags (or 1 to 1.5 60-pound bags) of fast-setting concrete per post hole. For 6x6 gate posts or corner posts supporting heavy tension, dig a 12-inch diameter hole and use 3 to 4 bags.

Standard 6-foot tall privacy fences require 3 horizontal 2x4 rails per 8-foot bay (top, middle, and bottom) to prevent picket warping and bowing. Shorter 4-foot fences require 2 rails. For 5.5-inch wide dog-ear pickets with no spacing gap, calculate 1.74 pickets per linear foot (approximately 14 pickets per 8-foot section). For 3.5-inch pickets, calculate 2.74 pickets per linear foot.

The clear width of any walk-through or double drive gates (typically 3 to 4 feet for pedestrian gates, 8 to 12 feet for vehicle gates) must be subtracted from the linear footage when estimating pickets and rails. However, gates require dedicated heavy-duty hinge and latch posts (often 6x6 timbers or thick-walled steel posts) set deeper in concrete to support swinging dynamic torque.