Carpentry & Framing
Calculate fence posts, 2x4 horizontal rails, dog-ear pickets, post-hole concrete bags, and gate hardware for privacy and picket fences.
Enter total fence length, fence height, post spacing, picket width, and gate count. The calculator figures line and corner posts, horizontal rails, vertical pickets, and 50-lb concrete bags.
Calculation and worked example reviewed 2026-11-14. See our calculation methodology.
Framing: 15 posts (8' OC, 13 bays) + 39 horizontal 2×4 rails (3 per section).
Infill & foundation: 220 pickets (5.5" wide, 5% waste) · 30 bags (50 lb) fast-setting concrete (2 bags/post).
Formula and example
This estimator converts your entered jobsite inputs (total fence length, fence height, post spacing on-center, picket face width, picket spacing gap, number of walk gates, picket waste & cut allowance) into consistent US trade units, computes the exact geometric baseline first, and then applies any selected waste or order allowance so you can verify both numbers before purchasing materials.
where:
Sections = ceil(fence length ÷ post spacing); posts = sections + 1 + (gates × 1); rails per section = (height >= 6 ? 3 : 2); rails = sections × rails per section; pickets = ceil((fence length × 12) ÷ (picket width + gap)) × (1 + waste% ÷ 100); concrete bags (50 lb) = posts × 2.
A 100 ft privacy fence (6 ft height) with 8 ft post spacing, 3 rails, and 5.5 in dog-ear pickets (with 1/4 in gap) requires 14 posts, 39 horizontal 2×4 rails, 220 pickets (with 5% waste), and 28 bags (50 lb) of concrete for post holes.
Calculations include 4×4 posts, three 2×4 horizontal rails, 5.5 in dog-ear pickets (1/4 in gap), and 2 concrete bags/post.
| Fence Run Length | Line & End Posts | Horizontal 2×4 Rails | Pickets (w/ 5% waste) |
|---|---|---|---|
| 50 ft backyard run | 8 posts (16 bags) | 21 rails (7 bays × 3) | 110 pickets |
| 100 ft property line | 14 posts (28 bags) | 39 rails (13 bays × 3) | 220 pickets |
| 150 ft perimeter | 20 posts (40 bags) | 57 rails (19 bays × 3) | 330 pickets |
| 200 ft perimeter | 26 posts (52 bags) | 75 rails (25 bays × 3) | 440 pickets |
Assumes level or uniformly sloped ground using standard wood post-and-rail construction. Stepped racking on steep grades, masonry retaining walls, custom decorative shadowbox patterns, or high-wind coastal engineering require site-specific structural plans.
As a standard rule of thumb, dig post holes to a depth of 1/3 to 1/2 of the fence's above-ground height. For a 6-foot privacy fence, dig at least 24 to 36 inches deep (below your local regional frost line) to ensure posts do not lean over time.
A standard 4×4 wood post in an 8- to 10-inch diameter hole requires two 50-pound bags of fast-setting concrete. Heavier 6×6 corner posts or gate hinge posts in 12-inch holes typically require 3 to 4 bags.
Building codes and industry best practices recommend three 2×4 horizontal rails (top, middle, and bottom) for any fence 6 feet or taller. Three rails prevent thin 5/8-inch pickets from twisting, warping, or pulling loose in summer heat.
Pressure-treated pine pickets are saturated with water preservative from the factory and will shrink roughly 1/8 to 1/4 inch as they dry in the sun, so they can be butted tight. Dry western red cedar pickets should be installed with an intentional 1/8 to 1/4 inch gap to allow for wet-weather moisture expansion.
Method references: AFA: American Fence Association residential guidelines