Fence & Lumber Calculator
Calculate posts, rails, pickets, and concrete needed for any wood fence project.
I calculated materials for a backyard fence project before running this kind of tool and ended up making three extra hardware store trips. Having post count, rail count, and picket count in one place before you start saves a lot of time and over-buying.
Posts are typically set 8 feet apart on center. Each section uses rails spanning between posts. Always add 10% to picket counts, you'll need cuts for ends and to replace damaged boards during installation.
Post spacing and structural considerations
Standard post spacing for residential wood fences is 6–8 feet on center. Six-foot spacing is stronger and better for heavy privacy fences or areas with high wind exposure. Eight-foot spacing uses fewer posts and is adequate for standard 6-foot privacy fences in typical conditions. Gate openings require double posts (one on each side of the gate) regardless of spacing, so account for those separately.
Post depth and concrete
Standard guidance: bury at least 1/3 of the post length. A 6-foot fence uses an 8-foot post (2 feet in ground, 6 feet above). In frost-prone climates, posts must extend below the frost line, typically 36–42 inches in northern US states. One 50-lb bag of fast-setting concrete per post is standard for residential fence posts (approximately 0.375 cubic feet per bag).
Rail count
Two rails are standard for most residential privacy fences: one near the top and one near the bottom of the fence. Three rails add rigidity for taller fences (6+ feet) and reduces picket flex. Gate sections always benefit from a third diagonal brace rail to prevent sagging.
Picket calculation
Pickets are calculated from total fence length and the effective width of each picket (actual width plus gap). The calculation gives the number of pickets needed. Always add a waste factor, pickets at the ends of each section require cuts, and some boards will have defects. Ordering 10% extra ensures you finish without an extra store run.
Frequently asked questions
What wood species is best for fencing?
Pressure-treated pine is the most cost-effective and durable option. Cedar is naturally rot-resistant and more attractive but costs 2–3x more. Redwood is similar to cedar in properties. Composite and vinyl fence materials require no painting or staining and have much longer lifespans, but cost significantly more upfront.
Do I need permits for a fence?
Most jurisdictions require permits for fences above a certain height (often 6 feet). HOAs may have additional restrictions on style, color, and placement. Call 811 (the national "call before you dig" number) before digging any post holes, underground utility strikes are dangerous and legally your responsibility if you don't call first.
How deep should post holes be?
The general rule is 1/3 of the post height plus 6 inches below frost line. In non-frost climates, 24–30 inches is standard for an 8-foot post. In frost zones, dig below the local frost depth, check your county's frost line, which ranges from 12 inches in the South to 60+ inches in Minnesota.