Fence Calculator — Posts, Rails, Pickets & Concrete

How Many Fence Posts Do I Need?

A fence post count follows a single rule across every style, material, and code jurisdiction in the United States: divide the fence length by the post spacing and add 1 for the end of the run. A 100-foot run at 8-foot on-center spacing needs 13 sections and therefore 14 posts. Using 6-foot spacing pushes the count to 18 posts — a meaningful labor and concrete difference that earns its cost on fences over 6 feet tall or in high-wind zones.

How Many Fence Rails Do I Need?

Fence rails follow the height-driven rule of 1 rail per 24 inches of fence height, rounded up, with a minimum of 2. A 6-foot fence uses 3 rails per section (top, middle, bottom); an 8-foot fence uses 4. Multiply rails per section by section count to get the total. On a 100-foot run at 8-foot spacing, that is 13 sections × 3 rails = 39 rails for a 6-foot fence. Order an additional rail per 50 feet to replace any with bow or knot-line cracks found at delivery.

How Many Fence Pickets Do I Need?

Picket count uses one of two formulas depending on style. For a privacy fence with boards butted tight, divide the fence run in inches by the actual picket width — 5.5 inches for a 1×6 board. For a picket-style fence with a visible gap, divide by the combined picket width plus the gap. A 100-foot run of butted 1×6 privacy pickets is 218 boards; add 10% waste to get 240. A classic picket at 3.5 inches wide with a 2.5-inch gap is 200 pickets for the same run.

How to Account for Gates in Your Material Count

Every contractor has watched a homeowner buy lumber for a 150-foot fence on a 142-foot run with a 4-foot gate and a 4-foot extra — 12 too many pickets and two too many rails because gate width was not deducted from the run. Subtract total gate width from fence length before you calculate rails and pickets. Gate-side posts are already counted in the post total, so the post count does not change. A fence gate opening deserves 4×6 posts flanking it — 4×4 posts sag within five years under the repeated hinge load.

Tips for Ordering Lumber — Waste and Round-Up Rules

Apply a waste factor of 10% for residential layouts with 3–4 corners, 5% for simple rectangular yards, and 15% for complex perimeters or rocky sites. Pickets ship in bundles of 8 or 16; round orders to the next full bundle to avoid a return trip. Cull lumber at the yard — expect one or two boards replaced on a 200-foot fence due to knots or splits discovered after bundle-opening.

Project Size Reference Table — By Lot Size

Assumes square lot, rectangular perimeter, and 10% waste factor applied to board count. Rails rounded to whole units. Subtract one post span plus its rails and boards for each gate.

Accounting for Gates — Subtract Before You Calculate

A 150-foot run with two 4-foot walk gates carries an effective run of 142 feet for picket and rail purposes. The post total stays at 20 (gate-side posts are still needed), but pickets drop from 327 to 310 and rails drop from 57 to 54. This is the single most common material over-order mistake in residential fencing — confirmed across two top Reddit and ContractorTalk threads captured in the research artifacts for this page.

Irregular Lots — Divide Into Segments

For L-shaped, trapezoidal, or curved lots, divide the perimeter into straight segments and calculate each segment separately. Corner posts are shared between segments, so count each corner post once and add 1 end post only at the terminal ends of the complete run. Record each segment length on your site plan before you order — a 200-foot perimeter split as 80+60+60 foot segments is materially different from a 200-foot straight run in post placement.

The 1/3 Rule — Post Length to Burial Depth

Bury at least one-third of the total post length below grade. A 6-foot fence needs posts at least 8 feet long (2 feet buried + 6 feet exposed); a 4-foot fence needs 6-foot posts. In frost-prone regions, the frost line rule overrides the one-third rule whenever it calls for deeper footing — fences in Chicago need 42-inch burial, not 24, because the IRC R403.1 frost-line floor is 40 inches in that climate zone.

Frost-Line Depth by US Region

Sources: IRC R403.1 (2021) · USDA Frost Depth Maps · NOAA Climate Zones. Always verify with your local AHJ.

Concrete for Post Holes — How Many Bags per Post

A standard residential fence post uses 2 bags of 60-lb fast-setting concrete for a 10-inch-diameter, 36-inch-deep hole. Scale up to 3 bags per post for 12-inch holes or posts over 8 feet tall. For large projects or non-standard holes, use our post hole concrete calculator for precise volume per hole. Larger projects needing more than 10 bags benefit from the full concrete calculator, which allows custom mix ratios and bag sizes.

Pressure-Treated Pine

Pressure-treated southern yellow pine is the default residential fence material — lowest cost per linear foot, widely stocked, and treated to UC4B or UC4A for ground contact. Expect 15–20 years of service on buried posts and 20–25 on rails. Allow treated lumber to dry for 2–4 weeks before staining. Pressure-treated pine is the recommended species for every post in ground contact regardless of the picket or rail species above grade.

Cedar

Western red cedar resists rot and insects without chemical treatment, carries a warm reddish color that silvers gracefully, and holds stain well. Use cedar for rails and pickets above grade; do not use untreated cedar for posts in ground contact. Life expectancy is 20–30 years above grade. Cedar is typically 40–60% more expensive per linear foot than pressure-treated pine.

Redwood

Redwood carries the highest natural rot and insect resistance, the most dimensional stability, and the premium price tag. Availability drops sharply outside the West Coast. Life expectancy is 25–30 years above grade. Reserve redwood for visible pickets and rails; use pressure-treated pine for posts.

Fence Styles and Their Board Counts

Board counts derived from the picket formula at 5.5-inch picket width; shadow-box and board-on-board apply a 1.5× multiplier per the alternating / overlapping layout. Relative cost indexed to a straight 1×6 privacy run.

Lumber Species Comparison

When a Permit Is Required

IRC R105.1 exempts fences under 7 feet tall from permit in many jurisdictions, but local amendments often push the threshold lower. Common triggers include: height over 6 feet, chain link in residential zones, any fence on a property line, and any fence in a historic district. Call your city or county building department before ordering materials — a failed permit inspection can require demolition.

HOA Height and Setback Rules

Homeowner associations often impose stricter rules than local code. Typical HOA limits: 6-foot maximum in backyards, 4-foot maximum in front yards, 1–3 feet of setback from the property line, pre-approved styles only (privacy, shadow-box, picket), and a 30–60 day written-approval requirement before construction begins. Submit plans in writing and keep the approval letter.

Pre-Build Checklist

Cost by Fence Type (2026)

Sources: RS Means 2026 construction data · HomeGuide 2026 · Angi 2026 · CalcSummit 2026 regional dataset. Labor is 50–65% of installed cost. Regional variation ±15% from these midpoints.

What Affects Fence Cost

Four variables drive residential fence cost more than material choice: post depth (deeper holes add time and concrete), wood species (cedar and redwood run 40–80% above pressure-treated pine), gate count (each gate adds $200–$500 in hardware and framing), and terrain (rocky, sloped, or wooded sites add 15–30% in labor). Pull the 2026 installed range from the table above and adjust by these factors. For a metal-perimeter project, our chain link fence calculator returns posts, top rail, mesh, and tension wire per linear foot at the lower end of this cost band.

DIY vs. Hired Installation — Cost Difference

DIY fence installation saves 50–65% on labor for a straightforward perimeter — a 200-foot privacy fence that costs $7,200 installed by a contractor runs $2,500–$3,000 in materials alone. Budget 2–3 full weekends for a two-person crew on a 200-foot project with 2 gates. For a full cost breakdown including regional labor rates, use our fence cost calculator.