Fence Supply Calculator: How to Estimate Materials

A fence supply calculator works out the amount of fencing materials you need for a project: it takes your fence length, height, and post spacing, then returns the number of posts, rails, pickets, and fasteners required. You enter your measurements in feet or meters, and the calculator gives you a full material list with quantities. This guide explains the math behind the calculator, how to use it, and what to watch out for so you order the right amount the first time.

Formula

The calculator uses simple arithmetic based on standard fence construction. For a straight fence line:

• Number of posts = ceil(length / post_spacing) + 1 — the +1 accounts for the end post. If your fence has corners or gates, add extra posts accordingly.
• Total rail length = number_of_rails × fence_length — this is the linear feet of horizontal rails, not accounting for waste or overlap.
• Number of pickets = ceil(fence_length × 12 / (picket_width + picket_gap)) — converts feet to inches, then divides by the combined width of one picket plus the gap.
• Concrete per post = 50 lb per post for a typical 4-inch-diameter post hole, but this varies with hole size and soil.

All variables are in consistent units: length (ft), height (ft), post spacing (ft), rails (count), picket width (in), picket gap (in). The calculator outputs counts (posts, pickets) and lengths (rail feet).

Worked Example

Using the default values: fence length = 100 ft, height = 6 ft, post spacing = 8 ft, 3 rails, picket width = 5.5 in, picket gap = 0.5 in.

1. Posts: 100 / 8 = 12.5, round up to 13, plus 1 = 14 posts.
2. Rails: 3 rails × 100 ft = 300 linear feet of rail material.
3. Pickets: 100 × 12 = 1200 inches. 5.5 + 0.5 = 6 inches per picket+gap. 1200 / 6 = 200 pickets exactly.
4. Concrete: 14 posts × 50 lb = 700 lb of concrete mix (about 14 bags of 50 lb).

The calculator returns 14 posts, 300 ft of rails, 200 pickets, and 50 lb per post. These match the manual calculation.

When to Use a Fence Supply Calculator

Use this calculator when you are planning a new fence, replacing sections, or getting quotes from contractors. It helps you:

• Create a material list for a home improvement store order.
• Compare costs of different post spacings or picket widths.
• Check that a contractor’s estimate includes enough materials.
• Budget for concrete, nails, and other fasteners.

The calculator works for standard wood privacy fences, chain-link, and vinyl fences, but you’ll need to adjust for each type. For chain-link, you don’t need pickets—you need fabric rolls and tension wire. For vinyl, panels come in fixed widths, so you calculate panels instead of pickets.

How to Choose Input Values

Your inputs directly affect the result, so measure carefully and choose realistic defaults.

• Fence length: Measure the exact linear feet of the fence line, not the property perimeter. Use a measuring wheel or tape, and account for slopes (a slope increases the actual surface length).
• Post spacing: Common spacings are 6, 8, or 10 feet. Tighter spacing (6 ft) is stronger but costs more. For wood fences, 8 ft is typical; for vinyl, follow manufacturer specs.
• Number of rails: For a 4-ft fence, 2 rails are common; for 6-ft, 3 rails; for 8-ft, 4 rails. Some designs use a top and bottom rail only, but that leaves a gap in the middle.
• Picket width and gap: Standard picket is 5.5 in wide (a 1×6 board). Gaps range from 0 (board-on-board) to 1 inch or more for a semi-private fence. The gap dramatically changes picket count.

When in doubt, round up to the next whole number. It’s cheaper to return a few extra boards than to make a second trip.

Common Mistakes and How to Avoid Them

Even with a calculator, people make errors. Here are the most frequent:

• Mixing units: Entering length in feet but picket width in inches without converting. The calculator handles that, but if you do it manually, convert everything to inches or feet first.
• Forgetting the +1 for posts: The end post is easy to miss. For a 100-ft fence with 8-ft spacing, you need 13 intervals but 14 posts.
• Ignoring waste: Wood boards can be warped, cracked, or cut wrong. Add 5–10% extra for pickets and rails, especially if you’re cutting around obstacles.
• Not accounting for gates: A gate needs extra posts on each side, and the gate opening removes pickets and rails. Subtract the gate width from the fence length first.
• Post hole depth: Concrete per post depends on hole depth and diameter. A typical 6-ft post needs a hole 24–30 inches deep and 8–10 inches wide, requiring roughly 50–60 lb of concrete. Check local frost depth.

Limitations of the Calculator

This calculator gives a solid estimate, but it can’t account for everything:

• Terrain: Sloped ground requires stepped or racked panels, which may need more material.
• Obstacles: Trees, rocks, or utilities may force you to adjust post spacing.
• Local codes: Some areas have height limits, setback rules, or require specific post depths. Check with your local building department.
• Material type: The calculator assumes uniform pickets and rails. Chain-link, aluminum, or composite panels have different requirements.
• Fasteners and hardware: Nails, screws, brackets, and post caps are not included. A rule of thumb is 2–3 lb of nails per 100 pickets, but that varies.

Cost Considerations

Material costs vary widely by region and wood type. To estimate cost, multiply the quantities by local prices:

• Posts: pressure-treated pine is cheaper than cedar or composite.
• Pickets: cedar is common for privacy fences; redwood costs more.
• Concrete: a 50-lb bag of fast-setting mix costs a few dollars.
• Rails: often the same wood as pickets, but longer boards (8 or 16 ft) may be cheaper per foot.

Don’t forget delivery fees if you order in bulk, and sales tax. For a 100-ft, 6-ft cedar fence, materials alone might run $1,500–$3,000, but labor can double that if you hire a contractor.

Frequently Asked Questions

How many pickets do I need for a 100-foot fence?

With 5.5-inch pickets and a 0.5-inch gap, you need 200 pickets (as shown in the example). If you use a 1-inch gap, the count drops to about 185. If you use no gap (board-on-board), you’ll need about 218 pickets because each board overlaps the next.

How deep should fence posts be?

A general rule is to bury one-third of the post height. For a 6-ft post, that’s 2 ft deep. In cold climates, the hole must go below the frost line to prevent heaving. The hole diameter should be about three times the post width—for a 4×4 post, that’s 8–12 inches.

Do I need concrete for every fence post?

Concrete adds stability, but in sandy soil you may need it more than in clay. Some builders use gravel and tamped dirt for economy, but concrete is recommended for gate posts and corner posts. For a typical wood fence, most homeowners use concrete for all posts.

How much concrete per post?

For a 4×4 post with a 10-inch-diameter hole, 2 ft deep, you’ll need about 50–60 lb of dry mix per post. That’s one 50-lb bag or two 30-lb bags. For larger holes or deeper posts, use more—calculate volume using the cylinder formula (π × radius² × depth) and convert to bags.

What is the best post spacing for a wood fence?

Eight feet is standard for most residential wood fences. Six-foot spacing is stronger and reduces sagging but adds about 20% more posts, increasing cost. Ten-foot spacing is possible with heavier rails but may sag over time. Follow local codes and manufacturer recommendations if using vinyl.

Should I buy extra material?

Yes, add 5–10% to your picket and rail counts to cover waste from cuts, warped boards, and mistakes. For a 200-picket fence, that’s 10–20 extra boards. It’s also wise to keep a few spare boards for future repairs.

Related

• Drywall Estimator Calculator: How It Works
• Drywall Framing Calculator: Studs & Sheets
• Drywall Grid Calculator: How to Estimate Framing

in l | Fence length | ft | 100 | 0
in h | Fence height | ft | 6 | 0
in ps | Post spacing | ft | 8 | 1
in rn | Number of rails | - | 3 | 1
in pw | Picket width | in | 5.5 | 1
in pg | Picket gap | in | 0.5 | 0
out posts | Number of posts | posts | ceil(l / ps) + 1 | 0
out rails | Total rail length | ft | rn * l | 0
out pickets | Number of pickets | pickets | ceil(l * 12 / (pw + pg)) | 0
out concrete | Concrete per post | lb | 50 | 0