How many fence posts do I need for 100 feet of fence?

For 100 feet of fence with 8-foot post spacing, you need 13 posts (floor(100 ÷ 8) + 1 = 12 + 1). That gives you 12 sections of 8 feet each. If you use 6-foot spacing, you'll need 17 posts and 16 sections. Always add one extra post because the first post anchors the start of the run.

What is the standard fence post spacing?

Standard wood fence post spacing is 8 feet on center for most privacy and picket fences, which matches the length of standard fence panels sold at lumber yards. Chain-link fences typically use 10-foot spacing because the wire mesh handles the lateral load between posts. For vinyl fences, follow manufacturer specifications — some panels require exactly 6 or 8 feet.

How deep should fence posts be set?

Fence posts should be set at least 1/3 of their total length underground, with a minimum depth of 2 feet. For a 6-foot privacy fence using 8-foot posts, the bottom 2.5–3 feet should be in the ground. In cold climates, posts must extend below the frost line — typically 36–48 inches in northern states — to prevent heaving. Check local building codes for frost-depth requirements.

How much concrete do I need per fence post?

Most fence posts require 1–2 bags of 80-lb concrete. A 10-inch diameter hole that is 36 inches deep holds about 1.4 cubic feet of concrete, which equals roughly 2 bags of 80-lb mix. Smaller holes (8 inches, 24 inches deep) need about 1 bag per post. Use the calculator above to get an exact bag count based on your actual hole dimensions.

How many pickets do I need per fence section?

For a standard 8-foot fence section using 3.5-inch pickets with a 0.5-inch gap, you need about 24 pickets per section (floor(8 ft ÷ (4 in ÷ 12)) = 24). Tighter gaps or narrower pickets increase the count. Our calculator uses the actual picket width and gap you enter, so you get exact results instead of rough estimates.

Do I need a permit for a fence?

Most municipalities require a building permit for fences over 4–6 feet tall. Permit costs typically range from $20–$100 depending on jurisdiction. Front yard fences face stricter height limits than backyard fences in most areas. HOA communities often have additional restrictions on materials and colors. Always check with your local building department before digging post holes — unpermitted fences may need to be removed at your expense.

How long does a wood fence last?

Pressure-treated pine fencing typically lasts 15–20 years with basic maintenance (staining or sealing every 2–3 years). Cedar and redwood fences last 20–30 years because their natural oils resist rot and insects without chemical treatment. Vinyl (PVC) fences last 20–30 years and require almost no maintenance beyond occasional washing. The biggest factor in fence longevity is post installation — posts set in concrete below the frost line with proper drainage outlast posts set in soil alone by 5–10 years.

What is the cheapest type of fence?

Chain-link fencing is the most affordable option at $8–$18 per linear foot installed, but it provides no privacy. For privacy fencing, pressure-treated pine is the most economical choice at $15–$30/lf installed. Split-rail fencing ($10–$20/lf) is low cost but open. Vinyl and aluminum fencing cost more upfront ($25–$50/lf) but require less maintenance over their lifespan, often making them more economical in the long run for homeowners planning to stay 15+ years.

Fence Calculator — Posts, Rails, Pickets & Cost

Estimates posts, rails, pickets, concrete bags, and cost for wood privacy fences.

What Is a Fence? Types, Heights, and Material Guide

This fence calculator estimates post count, rails, pickets, concrete bags, and material cost for any fencing project. A fence is a barrier or enclosure built from posts, rails, and facing material (pickets, boards, mesh, or panels) to define property boundaries, provide privacy, contain pets or children, or enhance curb appeal. In the United States, approximately 35 million homeowners have some form of fencing — making it one of the most common residential construction projects.

Common fence types and their best uses:

Wood privacy fence — 6 ft tall with solid dog-ear pickets; the most popular residential choice; pressure-treated pine costs $15–$30 per linear foot installed; lifespan 15–20 years
Cedar or redwood fence — naturally rot-resistant; similar height and style options; $25–$45/lf installed; lasts 20–30 years with periodic staining
Vinyl (PVC) fence — low maintenance, never needs painting; $25–$40/lf installed; warranties up to 20–30 years; less strong than wood in high winds
Chain-link fence — the most economical option at $10–$20/lf installed; durable but provides no privacy; ideal for securing yards and containing pets
Aluminum / wrought iron — decorative and long-lasting; $25–$50/lf installed; excellent for front yards and pool enclosures; requires minimal maintenance
Split rail fence — low, open-style fence; $10–$20/lf installed; good for marking boundaries and acreage without blocking views

Before installing any fence, check your local regulations:

Building permits — most municipalities require a permit for fences over 4–6 feet; permit costs range from $20–$100 depending on jurisdiction
HOA restrictions — homeowner associations often specify height limits, material types, and colors; always confirm before purchasing materials
Setback requirements — most jurisdictions require fences to be set back 1–2 feet from the property line, especially in front yards
Call 811 before digging — required by law; free utility location service prevents damage to underground lines

How to Calculate Fence Posts and Materials

Calculating fence materials starts with two numbers: total fence length and post spacing. The formula is straightforward — divide the total length by the post spacing, then add one post to cap the end of the run. A 100-foot fence with 8-foot spacing needs floor(100 ÷ 8) + 1 = 13 posts and 12 sections. From there, multiply sections by rails per section to get your rail count, and use the picket width and gap to calculate how many pickets fill each section.

The complete material list for any wood privacy fence includes posts, rails, pickets, and concrete for setting the posts. Our fence post concrete calculator handles the concrete estimate separately, but this tool combines all four into one calculation.

Post Spacing — Standard Distances and When to Go Closer

The standard post spacing for a wood privacy fence is 8 feet on center. This matches the length of pre-built fence panels and 8-foot dimensional lumber, so material waste is minimal. Chain-link fences can go up to 10 feet between posts because the wire provides its own lateral support. Vinyl fence systems vary by manufacturer — most specify exactly 6 or 8 feet.

Use closer spacing (6 feet) when the fence must withstand high wind loads, when the fence is taller than 6 feet, or when the soil is soft or sandy and posts are less stable. Wider spacing (10 feet) works for temporary or lightweight fences. For a standard 6-foot wood privacy fence in most US climates, 8-foot spacing is the correct default.

Post Sizing by Fence Height

4-foot fence — 6-foot posts, 2 feet in ground
6-foot fence — 8-foot posts, 2.5–3 feet in ground
8-foot fence — 10-foot posts, 3 feet in ground (check local codes)

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Rails and Pickets — Wood Fence Material Breakdown

Each fence section consists of horizontal rails that span between posts and vertical pickets nailed to those rails. Most privacy fences use 2 rails per section for fences up to 5 feet tall, and 3 rails for fences 6 feet or taller. Three rails provide better rigidity and prevent pickets from warping or bowing over time.

Standard dog-ear pickets are 3.5 inches wide (a 1×4 board has a nominal 4-inch width and an actual 3.5-inch width). For a privacy fence, gaps between pickets are typically 0–0.5 inches. Wider gaps (2–3 inches) create the classic open picket look. A single 8-foot section with 3.5-inch pickets and 0.5-inch gaps requires exactly 24 pickets.

Common Wood Species for Fence Pickets

Pressure-treated pine — most affordable, lasts 15–20 years, requires sealing
Cedar — naturally rot-resistant, attractive grain, lasts 20–30 years
Redwood — premium option, excellent rot resistance, regional availability
Composite — no painting or staining, higher upfront cost, 25+ year lifespan

Fence Cost Estimates by Material

Material costs for a 100-foot wood privacy fence vary widely by species and region, but these ranges are typical for 2026:

Pressure-treated pine pickets — $1.50–$2.50 each
Cedar pickets — $2.50–$4.00 each
4×4×8 fence posts — $8–$15 each (pressure-treated)
2×4×8 rails — $4–$7 each
80-lb concrete bags — $6–$9 each
Total materials, 100 ft of 6-ft cedar privacy fence — $800–$1,800

Professional installation typically adds $15–$30 per linear foot on top of materials, bringing an installed 100-foot cedar fence to $2,300–$4,800 total. DIY installation saves the labor cost but requires post-hole digger rental at $60–$100/day.

Fence Post Concrete — How Much Do You Need?

The amount of concrete needed per post depends on hole diameter and depth. The formula is: hole volume (ft³) = π × (diameter ÷ 2)² × depth. An 80-lb bag of Quikrete yields roughly 0.6 cubic feet when mixed, so divide the hole volume by 0.6 and round up to get your bag count.

For a 10-inch diameter hole that is 36 inches (3 feet) deep: volume = π × (0.417 ft)² × 3 ft = 1.64 ft³ ÷ 0.6 = 2.73, which rounds up to 3 bags per post. Our calculator does this automatically for every post in your fence. For a deeper dive into concrete quantities, see our concrete bag calculator and our post hole calculator.

Concrete Setting Methods

Dry-set (fast) — pour dry Quikrete into the hole, add water on top. Reaches working strength in 20–40 minutes.
Pre-mixed (traditional) — mix in a bucket or wheelbarrow, pour into hole. More control over consistency.
Foam set — expanding foam product (e.g. Sika Post Fix) replaces concrete. Fast and lightweight, but not approved for all fence types.

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Sources & References

IRC Section R403: Footings — International Residential Code — International Code Council
ACI 318-19: Building Code Requirements for Structural Concrete — American Concrete Institute
National Design Specification (NDS) for Wood Construction — American Wood Council

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