About This Tool
Building a fence requires precise material calculations to avoid costly overages or project delays from running short. Whether you're installing a privacy fence for backyard seclusion, a classic picket fence for curb appeal, or a shadowbox design that balances privacy with airflow, knowing exactly how many posts, rails, pickets, and concrete bags you need saves time and money. The standard approach of estimating materials by eye or rough guesswork leads to expensive mistakes: ordering too few posts means paying delivery fees twice, while excess pickets create waste and storage headaches. Our fence calculator eliminates guesswork by converting your fence length, height, and spacing preferences into precise material counts. The tool accounts for proper post spacing (typically 6-10 feet depending on fence type and terrain), rail requirements based on height (2 rails for shorter fences, 3 for taller ones), picket spacing that matches your chosen style, and the concrete needed to secure each post. Different fence styles serve different purposes: privacy fences use boards with zero gaps for complete screening, picket fences feature 1-2 inch gaps for decorative openness, and shadowbox fences alternate boards on both sides for semi-privacy with better wind resistance. Understanding your material requirements before purchasing ensures you get competitive quotes from suppliers and complete your fence installation without frustrating mid-project supply runs.
Post Spacing Guidelines
Proper post spacing forms the structural foundation of any fence. Too wide and your fence sags or fails in wind; too narrow wastes money on unnecessary materials.
Standard Spacing by Fence Type:
- 6-8 feet: Standard for most residential fences. This spacing provides adequate support for privacy, picket, and shadowbox styles on level ground. Most fence panels are manufactured in 6ft or 8ft widths to match this spacing.
- 6 feet: Use this tighter spacing for heavy privacy fences, areas with high wind exposure, or unstable soil. The extra posts increase stability and prevent sagging over time.
- 8-10 feet: Acceptable for lightweight picket fences on firm, level ground. This wider spacing reduces material costs but only works for fences under 4 feet tall with minimal wind load.
- Variable spacing: Slopes, corners, and irregular property lines require custom spacing. Always place posts at corners and grade changes, then space remaining posts evenly between these fixed points.
Post Specifications:
For a 6ft tall fence, use 4x4 posts that are 10ft long (8ft above ground + 2ft buried). Taller fences require longer posts: an 8ft fence needs 11-12ft posts buried 3ft deep. Pressure-treated lumber rated for ground contact is mandatory for buried portions. Cedar and redwood offer natural rot resistance but cost 2-3x more than treated pine.
Formula: Number of posts = (fence length ÷ post spacing) + 1. For example, a 100ft fence with 8ft spacing needs (100 ÷ 8) + 1 = 13.5, rounded up to 14 posts. Always round up to ensure you don't run short.
Fence Styles Explained
Choosing the right fence style balances aesthetics, privacy, cost, and maintenance. Each design serves distinct purposes:
Privacy Fence:
Boards installed vertically with zero gaps, creating complete visual screening. Requires 2 horizontal rails for fences up to 4ft, 3 rails for 5-8ft heights. The most material-intensive style, but provides maximum privacy and noise reduction. Commonly built at 6ft height (legal maximum in many jurisdictions without permits). Picket gap setting should be 0 inches. Annual cost for treated pine: $15-25 per linear foot installed.
Picket Fence:
Classic design with vertical pickets spaced 1-2 inches apart. This decorative style suits front yards and gardens where full privacy isn't needed. The gaps allow air circulation, reducing wind load and preventing the fence from acting like a sail in storms. Typically 3-4ft tall. Uses less lumber than privacy fences due to spacing, reducing costs by 20-30%. Picket gap setting: 1-2 inches.
Shadowbox Fence:
Alternating pickets on both sides of the rails create a fence that looks finished from both sides while providing semi-privacy. Boards overlap when viewed straight-on but reveal gaps at an angle, allowing airflow that reduces wind stress. This design is self-supporting in wind (air flows through rather than pushing against a solid wall). Costs 30-40% more than standard privacy due to double-sided picket installation. Picket gap setting: typically equal to picket width for balanced appearance.
Material Efficiency:
Privacy fences use the most pickets (boards touching with no gaps), picket fences use the least (wider spacing), and shadowbox falls in between but requires boards on both sides. Your picket gap setting directly impacts total material: a 100ft privacy fence with 5.5-inch boards and 0-inch gaps needs roughly 218 pickets, while the same fence with 1-inch gaps needs only 180 pickets, saving 40+ boards.
Post Depth and Concrete Requirements
Posts must be buried deep enough to resist frost heave, wind load, and ground movement. Improper depth causes leaning, rotting, or complete fence failure within 2-3 years.
Depth Requirements:
- Fences up to 6ft: Bury posts 2ft deep (1/3 of total post height). For a 6ft fence, use 8ft posts with 2ft underground.
- Fences 7-8ft: Bury posts 3ft deep. Taller fences catch more wind and require deeper anchoring.
- Frost line consideration: In northern climates, posts must extend below the frost line (12-48 inches depending on region) to prevent heaving. Check local building codes.
Concrete Requirements:
Each post needs approximately 2 bags of 60lb Quikrete or similar fast-setting concrete mix. This assumes standard 4x4 posts in 10-inch diameter holes. Larger posts (6x6) or deeper holes may require 3 bags per post.
Installation Best Practices:
- Dig holes 6 inches deeper than required depth: Add 6 inches of gravel at the bottom for drainage. This prevents water from pooling around the post base, which causes rot even in treated lumber.
- Make holes 3x the post width: A 4x4 post needs a 12-inch diameter hole (or use a 10-inch auger for speed). This provides room for concrete and ensures proper post alignment.
- Set posts in stages: Pour concrete around the first few posts, let them set for 24 hours, then use them as reference points to string guidelines for remaining posts. This ensures a perfectly straight fence line.
- Slope the concrete top: Angle the concrete away from the post to shed water. Standing water at the post-concrete junction accelerates rot.
Cost Estimate: At $5-6 per bag, concrete typically adds $10-12 per post to your project. For a 100ft fence with 14 posts, budget $140-170 for concrete alone.
Property Line Setbacks and Regulations
Building a fence without verifying property lines and local regulations invites legal disputes and costly reconstruction. Most municipalities regulate fence height, placement, and style.
Survey Your Property Line:
Never trust old fence lines, yard markers, or neighbor agreements. Order a professional survey ($300-600) or locate your property pins yourself using recorded plat maps from the county recorder's office. Building even 6 inches onto a neighbor's property gives them legal right to demand fence removal at your expense. Many installers build 6-12 inches inside the property line as a buffer against survey errors.
Height Restrictions:
- Backyard: Most jurisdictions allow 6ft fences without permits. Anything taller typically requires a variance or permit.
- Front yard: Height limits often drop to 3-4ft to preserve sight lines for traffic safety. Corner lots face stricter rules due to intersection visibility requirements.
- Pool fences: Many states mandate 4-5ft minimum height with self-closing, self-latching gates to prevent child drowning. These regulations override standard fence codes.
HOA Restrictions:
Homeowners associations often dictate fence materials, colors, styles, and even prohibit fences entirely in front yards. Review your CC&Rs (Covenants, Conditions & Restrictions) before purchasing materials. Violation enforcement can include fines or mandatory removal.
Easements and Utilities:
Utility easements (typically 5-15ft wide along property edges) prohibit permanent structures including fences. Call 811 before digging to locate underground utilities. Hitting a gas line during post installation can result in evacuation, service interruptions, and repair bills exceeding $10,000.
Good Neighbor Fence Laws:
Some states require the "finished side" (smooth side without visible rails and posts) to face neighbors. Shadowbox fences avoid this issue by looking identical from both sides. Before building on a shared property line, get written neighbor consent. Shared boundary fences may require cost splitting under state law.
Material Cost Estimation and Budgeting
Fence costs vary dramatically based on materials, labor, and site conditions. Understanding these factors helps you budget accurately and choose the best value option.
Material Costs (per linear foot):
- Pressure-treated pine: $15-25 installed (most economical, requires staining every 2-3 years)
- Cedar: $30-40 installed (naturally rot-resistant, weathers to gray without treatment)
- Vinyl: $25-35 installed (maintenance-free, never needs painting, but can crack in cold)
- Composite: $40-60 installed (eco-friendly recycled materials, 25+ year lifespan)
- Wrought iron: $25-35 per linear foot (decorative, see-through design, requires painting)
DIY Cost Breakdown (100ft privacy fence, 6ft tall, treated pine):
| Posts (14 × 4x4x8): | $210 |
| Rails (42 × 2x4x8): | $168 |
| Pickets (218 × 1x6x6): | $872 |
| Concrete (28 bags): | $168 |
| Hardware (screws, brackets, gate): | $150 |
| Total Materials: | $1,568 |
Add $800-1,200 for professional installation if not DIYing. Total installed cost: $2,400-2,800 ($24-28/linear foot).
Money-Saving Strategies:
- Buy in bulk: Purchase full lumber bundles (50-100 pieces) for 10-15% discounts versus individual board pricing.
- Time purchases strategically: Lumber prices peak in spring/summer. Buying materials in fall/winter can save 20-30%.
- Compare suppliers: Big box stores, local lumberyards, and fence specialty suppliers often have vastly different pricing. Get 3 quotes.
- Rent tools: A gas-powered auger rental ($50/day) digs 14 post holes in 2-3 hours versus 2 days of hand digging.
- Reuse corner posts: If replacing an old fence, existing corner posts may still be structurally sound. Reusing 4 corner posts saves $60-80.