Fence Post Calculator
A solid fence starts with properly set posts. This calculator gives you the complete material list: number of 4×4 posts (with the correct total length for burying), 50lb concrete bags per post, 2×4 horizontal rails, and picket count. The rule for post depth: bury at least 1/3 of the total post length, with a minimum of 2 feet. For a 6-foot privacy fence, use 8-foot posts set 2 feet in the ground. Post spacing affects cost significantly: 6-foot spacing uses more posts and more concrete but is stronger; 8-foot spacing is standard for most wood fences and matches pre-cut 8-foot rail lengths. The picket count uses a 1/4-inch gap between boards — standard for pressure-treated pine to allow for seasonal expansion.
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Top Pick4×4×8 Pressure-Treated Post — Home Depot~$14.98* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How far apart should fence posts be?
For a standard wood privacy fence, posts are set 6 or 8 feet apart. Six-foot spacing is more rigid and better for 6-foot-tall fences in windy areas. Eight-foot spacing is the most common for standard 6-foot wood fences and matches pre-cut rail lengths.
How many bags of concrete per fence post?
Plan for 2 bags of 50lb fast-setting concrete per post for a standard 4×4 post in average soil. In loose or sandy soil, use 3 bags. Posts in clay-heavy soil may need only 1–2 bags but require proper drainage to prevent rot.
Should fence posts be set in concrete or gravel?
Concrete is the most secure option and is standard for privacy and security fences. Gravel (compacted pea gravel) works for lighter decorative fences and allows drainage that reduces post rot. Never set wood posts in solid concrete without ensuring drainage — standing water accelerates decay at the ground line even with pressure-treated lumber.
How many pickets do I need for 100 linear feet of fence?
For a 6-foot privacy fence using 1×6 boards (5.5" actual) with 1/4" gaps, each board covers 5.75 inches. For 100 linear feet (1,200 inches) ÷ 5.75 = approximately 209 boards. Add 5% for waste and cut ends: about 220 boards total.