How many fence posts do I need?

Divide the total fence length by the post spacing and add 1 for the end post. For example, a 200-foot fence with 8-foot spacing needs ceil(200 ÷ 8) + 1 = 26 posts. Then add extra posts for each corner (where the fence changes direction) and each gate opening (2 gate posts per gate). A rectangular backyard with one gate typically requires 4 corner posts plus 2 gate posts in addition to the calculated line posts.

How many pickets for a 100-foot fence?

For 3-1/2" wide pickets with no gap (privacy fence), approximately 343 pickets. The formula is: total fence length in inches ÷ picket width = 1,200" ÷ 3.5" = 342.9, rounded up to 343. For spaced pickets with a 1-1/2" gap, the count drops to 1,200" ÷ (3.5" + 1.5") = 240 pickets. Always add your waste factor (typically 10%) to the final count — so 343 pickets becomes 378 after waste, and 240 becomes 264.

What is standard fence post spacing?

8 feet on center is standard for most wood privacy and picket fences. This spacing aligns with standard lumber lengths (8-foot and 16-foot rails), minimizing waste and simplifying construction. Use 6-foot spacing for vinyl or PVC fences, fences taller than 6 feet, or properties in high-wind regions where closer spacing reduces flex and increases structural rigidity. Some metal and chain-link fences use 10-foot spacing with tension wire for support.

How deep should fence posts be?

One-third of the total post length should be below ground. For a standard 6-foot above-ground fence, use 8-foot posts and set them 2 feet deep. For a 4-foot fence, use 6-foot posts buried 2 feet. Always add 6 inches of compacted gravel at the bottom of the hole for drainage before setting the post. In cold climates with deep frost lines, check your local code — some jurisdictions require post footings to extend below the frost line (typically 36–48 inches) to prevent heaving.

Should I use 2 or 3 rails?

2 rails work well for fences under 6 feet tall. For fences 6 feet or taller, use 3 rails to prevent pickets from bowing and to improve wind resistance. The third (middle) rail is positioned at the midpoint between the top and bottom rails. Three-rail construction adds roughly 33% more rail lumber to the project, but the improved rigidity and longevity are well worth the cost on tall fences that will face years of wind and weather.

How much concrete per fence post?

One 50-lb bag of fast-setting concrete for standard 4×4 posts in firm soil. Use two 50-lb bags per post for 6×6 posts, gate posts, corner posts, or posts set in soft or sandy soil. Each 50-lb bag of concrete mix yields approximately 0.375 cubic feet when mixed. A standard 10-inch diameter hole that is 24 inches deep requires about 0.9 cubic feet of concrete, which is slightly more than two 50-lb bags. Pre-mixed fast-setting concrete can be poured dry into the hole and wetted in place for faster installation.

How do I calculate fence boards for a sloped yard?

For stepped fences, calculate each level section separately — measure the run of each step and compute the picket count per section, then sum them all. Stepped fences use the same picket length for every section, so total pickets = number of sections × pickets per section. For racked (sloped) fences that follow the grade continuously, the total picket count is the same as a flat fence of the same length, but individual pickets may need to be trimmed to follow the slope. Add 10–15% waste for racked fences to account for angled cuts at the top and bottom of each picket.

Fence Calculator — Posts, Rails & Pickets

How to Use the Fence Calculator

How to Calculate Fence Materials

Fence material estimation relies on two core formulas: Posts = ceil(Total Fence Length ÷ Post Spacing) + 1 and Pickets = Fence Run ÷ (Picket Width + Gap). The first formula gives you the number of line posts along a straight run, including the end post. The second determines how many pickets (or boards) fill each section between posts. For example, a 200-foot fence with 8-foot post spacing requires ceil(200 ÷ 8) + 1 = 26 posts. If you're using standard 3-1/2" wide dog-ear pickets with no gap for a privacy fence, each 8-foot section needs 96" ÷ 3.5" = 27.4, rounded up to 28 pickets per section. With 25 sections between 26 posts, that's 25 × 28 = 700 pickets total. Enter your fence dimensions into this fence calculator and it handles the post count, picket quantity, rail length, concrete bags, and waste factor automatically — no manual counting required.

This calculator supports privacy fences, spaced picket fences, and board-on-board designs. Select your fence style, enter the total fence run, choose post spacing and picket dimensions, account for gates, and the calculator returns a complete materials list with quantities for posts, rails, pickets, concrete, and fasteners.

Post Spacing and Layout

Post spacing is the single most important decision in fence layout because it determines structural strength, material cost, and how much the fence will flex in wind. The two standard spacings are:

8 feet on center: The most common spacing for wood privacy fences. Works well with standard 8-foot and 16-foot rail lumber, minimizing waste. Provides adequate rigidity for fences up to 6 feet tall in moderate wind areas.
6 feet on center: Recommended for vinyl/PVC fences, high-wind regions, and tall fences (over 6 feet). Also required when using shorter or thinner rail stock. The tighter spacing significantly reduces flex and racking.

Beyond line posts, your layout must account for end posts (at each terminus of a fence run), corner posts (where the fence changes direction), and gate posts (which bear the weight and stress of gate hardware). Gate and corner posts are often upsized to 6×6 lumber instead of the standard 4×4 for added strength. Set all posts at a depth equal to one-third of the total post length below ground — for a fence that stands 6 feet above grade using 8-foot posts, the bottom 2 feet should be buried. Add a 6-inch gravel base beneath each post for drainage, and set posts in concrete for maximum stability.

Rail and Picket Options

Rails are the horizontal members that connect posts and support the pickets. Most fences use either two or three rails:

2 rails: Adequate for fences under 6 feet tall. Position the top rail 6 to 8 inches from the top of the pickets and the bottom rail 6 to 8 inches from the ground. This configuration uses less lumber and is faster to build.
3 rails: Recommended for fences 6 feet and taller. The middle rail prevents pickets from bowing or warping over time and adds significant wind resistance. Position the middle rail at the midpoint between top and bottom rails.

Pickets come in several standard sizes. 1×4 (3-1/2" actual) pickets are the most common for privacy fences — tight spacing with no gap creates a solid visual barrier. 1×6 (5-1/2" actual) boards cover faster but create a heavier, more expensive fence. Picket tops are available in dog-ear (angled corners), flat-top, pointed, and gothic profiles. For spaced picket fences, a gap of 1-1/2" to 2-1/2" between pickets is typical, reducing material cost by 25–40% compared to a full privacy design.

Gate Planning

Gates require careful planning because they affect post placement and material quantities. Standard gate widths are:

3 feet: Minimum width for pedestrian access. Suitable for side yard gates and garden entrances.
4 feet: Comfortable single gate width that accommodates wheelbarrows, lawn mowers, and most yard equipment.
Double gates (8–12 feet): Required for vehicle access, boat trailers, or large equipment. Each leaf is typically 4 to 6 feet wide. Use a drop rod or cane bolt on the stationary leaf to prevent sagging.

Gate posts must be set deeper and in larger-diameter concrete footings than standard line posts because they bear repeated lateral stress from swinging. Use heavy-duty strap hinges rated for the gate weight, and always install a cross-brace (diagonal 2×4) from the bottom hinge side to the top latch side to prevent the gate from sagging over time.

Pro Tips

Mark all post locations with a string line before digging. Drive stakes at each end of the fence run, stretch a taut line between them, and mark each post center along the string. This ensures a straight fence line and correct spacing.
Set corner and end posts first, then stretch a string between their tops for alignment. Set all intermediate line posts to this string — this method is faster and more accurate than setting posts one at a time with a level.
Post holes should be one-third of the total post length deep plus a 6-inch gravel base. The gravel allows water to drain away from the post bottom, which is the most common point of rot failure. Compact the gravel before setting the post.
Use pressure-treated lumber or cedar for all ground-contact components. Pressure-treated posts rated for ground contact (UC4A or UC4B) resist rot and insects for 20–25 years. Western red cedar is a naturally rot-resistant alternative that weathers to an attractive silver-gray patina.
Account for grade changes across the fence run. On sloped ground, you can either “step” the fence (each section drops in uniform increments) or “rack” the fence (pickets follow the slope angle continuously). Stepped fences are easier to build but leave triangular gaps at grade; racked fences look cleaner on gentle slopes but require angled rail cuts and custom picket lengths.

Free Fence Calculator — Posts, Rails & Pickets