Skip to main content
Kalcufy

Fence Calculator

Calculate posts, pickets, rails, concrete, and materials needed for wood, chain link, or vinyl fencing projects.

Reference table

Total Fence LengthTotal PostsPickets / BoardsRails
43 posts0 boards0 rails
54 posts3 boards2 rails
104 posts14 boards2 rails
155 posts24 boards4 rails
205 posts35 boards4 rails
256 posts46 boards6 rails
307 posts57 boards8 rails
408 posts79 boards10 rails
509 posts101 boards12 rails
6010 posts123 boards14 rails
7012 posts144 boards18 rails
7512 posts155 boards18 rails
8013 posts166 boards20 rails
9014 posts188 boards22 rails
10015 posts210 boards24 rails

Building Tips

  • Bury posts at least 1/3 of the total post length below ground. For a 6 ft fence, set posts 2 ft deep (8 ft total post length).
  • Use pressure-treated lumber rated for ground contact (UC4A or higher) for all posts. Standard pressure treatment is not rated for direct soil contact.
  • Place 3-4 inches of gravel at the bottom of each post hole for drainage before adding concrete. Standing water at the post base causes premature rot.
  • Let concrete cure 24-48 hours before attaching rails and pickets. Full cure takes 7 days — avoid heavy stress on posts during this period.

What Is a Fence Calculator?

A fence calculator estimates the exact number of posts, pickets (boards), rails, concrete bags, and fasteners needed for your fencing project. Rather than making rough guesses at the lumber yard, an accurate material list prevents costly return trips for missing materials or waste from over-buying. This calculator handles the geometry that trips up most DIYers: accounting for gate openings, calculating post depth based on fence height, adjusting picket count for different board widths and spacing, and estimating concrete volume for setting posts. It supports multiple fence styles including privacy (side-by-side boards), picket (spaced boards), and shadowbox (alternating boards on both sides). Whether you're fencing a small backyard or an entire property perimeter, accurate material estimates keep your project on budget and on schedule.

How Fence Material Estimation Works

The calculation starts with total fence length minus gate openings to get the effective fence length. Posts are then calculated by dividing the effective length by post spacing and adding 1 (for the end post), plus 2 extra posts per gate (gate posts are often 6×6 for hardware support). The number of sections equals posts minus 1. Rails per section (typically 2 for fences under 6 ft, 3 for 6-8 ft) are multiplied by sections for total rails. Pickets are calculated by dividing the total effective length (in inches) by the combined width of one picket plus one gap. For shadowbox style, the picket count is roughly doubled since boards are installed on alternating sides. Post length equals fence height plus burial depth — the standard rule is 1/3 of total post length underground, so a 6 ft fence uses 8 ft posts (6 ft above + 2 ft buried). Concrete per post depends on hole diameter (typically 3× post width) and depth, with 1-2 bags of 80 lb concrete mix per post being standard.

Key Building Considerations

  • Check local building codes and HOA rules before starting. Many municipalities require permits for fences over 4 ft and have setback requirements from property lines (often 2-6 inches).
  • Call 811 (free utility locating service) at least 48 hours before digging post holes. Hitting underground gas, water, or electric lines is dangerous and expensive.
  • Post spacing affects fence strength. 8 ft is standard for wood fences, but reduce to 6 ft in high-wind areas or for fences over 6 ft tall. Chain link can span up to 10 ft between posts.
  • Gate posts take the most stress. Use 6×6 posts for gates even if the rest of the fence uses 4×4. Set gate posts 6 inches deeper and use 2 bags of concrete instead of 1.
  • Pressure-treated wood needs 6-12 months to dry before staining. Apply a water-repellent preservative immediately after building, then stain the following year for best results.
  • Shadowbox fences use nearly double the pickets but provide privacy from both sides and look equally good from either side — important when local codes require the 'good side' to face neighbors.

Fence Styles & Uses

  • Privacy Fence (Side-by-Side): Boards placed flush with no gaps. Provides complete visual and wind blocking. Most popular residential style. 6 ft is the standard height for maximum privacy.
  • Picket Fence (Spaced): Boards with gaps for a decorative, open look. Classic American style at 3-4 ft height. Defines boundaries without blocking views or airflow.
  • Shadowbox (Board-on-Board): Alternating boards on both sides of the rails with slight overlap. Provides privacy while allowing airflow, reducing wind load. Looks equally finished from both sides.
  • Chain Link: Steel mesh fabric attached to metal posts. Most affordable per foot. Low maintenance. Available with privacy slats or vinyl coating. Best for property boundaries and pet containment.
  • Vinyl/PVC: Maintenance-free, never needs painting or staining. Resistant to rot, insects, and fading. Higher upfront cost but lowest lifetime cost. Available in privacy, semi-privacy, and picket styles.
  • Horizontal Board: Modern/contemporary style with boards running horizontally between posts. Uses the same materials as vertical fences but requires closer post spacing (6 ft max) to prevent board sagging.

Fence Calculation Examples

Step-by-step examples for common projects

100 ft Privacy Fence, 6 ft tall, 5.5" boards, 1 gate (4 ft)

  1. Effective length = 100 - (1 × 4) = 96 ft
  2. Posts = ceil(96 ÷ 8) + 1 + (1 × 2) = 12 + 1 + 2 = 15 posts
  3. Sections = 15 - 1 - 1 = 13 fence sections (excluding gate)
  4. Rails = 13 × 2 = 26 rails
  5. Pickets = ceil(96 × 12 ÷ 5.5) = ceil(209.5) = 210 boards
  6. Post length = 6 + 2 = 8 ft (1/3 buried)
  7. Concrete = 15 × 1.5 = ~23 bags (80 lb)

Buy 15 posts (8 ft), 210 boards, 26 rails, 23 concrete bags.

60 ft Shadowbox, 6 ft tall, 5.5" boards, 1.5" overlap

  1. Effective length = 60 ft (no gates)
  2. Posts = ceil(60 ÷ 8) + 1 = 8 + 1 = 9 posts
  3. Sections = 9 - 1 = 8 fence sections
  4. Rails = 8 × 3 = 24 rails
  5. Front pickets = ceil(60 × 12 ÷ (5.5 + 1.5)) = ceil(103) = 103
  6. Back pickets = ~103 (same count, alternating)
  7. Total pickets = 103 + 103 = 206 boards
  8. Concrete = 9 × 1.5 = ~14 bags

Buy 9 posts, 206 boards, 24 rails, 14 concrete bags.

Frequently Asked Questions

How deep should fence posts be buried?

The general rule is to bury 1/3 of the total post length. For a 6 ft fence, use 8 ft posts and bury 2 ft. For an 8 ft fence, use 12 ft posts and bury 4 ft (or at minimum 3 ft). In cold climates, posts should extend below the frost line to prevent heaving — check local building codes for your area's frost depth. Always place 3-4 inches of gravel at the bottom of the hole for drainage, then fill with concrete to within 1-2 inches of ground level, sloped away from the post to shed water.

How many bags of concrete per fence post?

For standard 4×4 posts in 8-inch diameter holes buried 24 inches deep, plan for 1 to 1.5 bags (80 lb) of pre-mixed concrete per post. For 6×6 gate posts or deeper holes, use 2 bags per post. A quick formula: a hole 8" wide × 24" deep uses about 0.6 cubic feet of concrete — one 80 lb bag yields approximately 0.6 cubic feet. If your soil is very sandy or loose, you may need slightly more to fill voids.

What's the best post spacing for a wood fence?

8 feet on center is the standard for most wood fences using standard 8-ft rails. This provides a good balance of strength, material efficiency, and appearance. In high-wind areas, heavy snow regions, or for fences over 6 ft tall, reduce spacing to 6 ft for added strength. Chain link fences can use 10 ft spacing because the mesh fabric distributes wind load across the entire fence rather than concentrating it on each section.

How do I calculate boards for a shadowbox fence?

A shadowbox fence has boards on both sides of the rails, offset so each side's boards cover the gaps of the other side. The total picket count is approximately double that of a standard privacy fence. Each side uses slightly fewer boards than a privacy fence because there's spacing between boards, but the two sides combined use more total wood. For example, if a privacy fence needs 200 boards, a shadowbox with 1.5" spacing between boards needs approximately 340-380 total boards (slightly less than double because of the spacing).

Should I use 4×4 or 6×6 fence posts?

4×4 posts (actual 3.5×3.5 inches) are standard for most residential fences up to 6 ft tall with 8 ft post spacing. Use 6×6 posts (actual 5.5×5.5 inches) for gate posts (they bear the most stress from gate weight and swinging), corner posts, fences over 6 ft tall, and in high-wind areas. Some builders use 6×6 for all posts on premium fences — the extra width provides significantly more strength and looks more substantial.

How do gates affect the material calculation?

Gates reduce the amount of fencing material needed (the gate opening doesn't need pickets or rails) but add posts. Each gate requires 2 dedicated gate posts — these are often 6×6 for strength, even if the rest of the fence uses 4×4. The calculator subtracts gate widths from the total fence length for picket and rail calculations, then adds 2 posts per gate. Gate hardware (hinges, latch, spring) is separate and typically costs $15-40 per gate for standard walk gates.

Sources