How the Calculator Counts Your Materials
The math follows how fences are actually built. Your fence length is divided by the post spacing to get the number of sections (rounded up), and posts = sections + 1 — the extra post is the one everyone forgets. Each section gets two rails under 6 feet of height or three rails at 6 feet and above, because tall privacy pickets warp without a middle rail. Pickets are counted by dividing the fence length by the true board width — a nominal "6-inch" picket is really 5.5 inches — then adding your waste factor for cuts, corners, and culls. Concrete is figured at two 50 lb fast-setting bags per post (three for 8-foot fences), the standard for a 4×4 post set 24 inches deep. Each gate adds a pair of hinges, a latch, and gate hardware but removes roughly one section of pickets and rails, which the calculator nets out for you.
Example: 150 ft Privacy Fence, 6 ft Tall, 8 ft Spacing
| Material | Quantity | How it's figured |
|---|---|---|
| Posts (4×4 × 8 ft) | 20 | 150 ÷ 8 = 19 sections, + 1 |
| Rails (2×4 × 8 ft) | 57 | 19 sections × 3 rails |
| Pickets (5.5 in × 6 ft) | 328 + waste | 150 ft × 12 ÷ 5.5 |
| Concrete (50 lb bags) | 40 | 20 posts × 2 bags |
At 5% waste, order about 345 pickets. Buying a full unit (bunk) of pickets is often cheaper than piecing the order together — ask the lumber desk. Compare what this fence costs in wood versus other materials with the fence cost estimator, or switch to the vinyl and chain link calculators.
Frequently Asked Questions
How far apart should fence posts be?
Eight feet is standard for wood privacy fences; six feet adds strength in windy areas or with heavier boards. Never exceed eight feet with wood rails — they sag over longer spans.
How many rails does a wood fence need?
Two per section under 6 feet of height, three for 6-foot and taller fences. The middle rail keeps long pickets from cupping and warping as they dry.
How many bags of concrete per post?
Two 50 lb bags of fast-setting concrete per 4×4 post set 24 inches deep is the rule of thumb. Go to three bags for 8-foot fences, sandy or loose soil, or high wind exposure.
Should pickets touch the ground?
No — leave about 2 inches of clearance. Ground contact wicks moisture into the boards and is the fastest way to rot a fence. Use a rot board (a horizontal 2×6 at grade) if you need to close the gap.
Can I embed this calculator on my website?
Yes — grab the free copy-paste snippet on our embed page. It's popular with fence contractors, lumber yards, and DIY blogs.