Fence Calculator

Calculate all the materials for your wood fence project: posts, rails, pickets, concrete, and hardware. Get a complete bill of materials with waste allowances so you can buy everything in one trip.

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Worked Example

A homeowner is building a 150 ft privacy fence, 6 ft tall, with 2 gates and 8 ft post spacing using 80-lb bags of concrete.

  1. 1 Fence length: 150 linear feet
  2. 2 Fence height: 6 ft (privacy style)
  3. 3 Post spacing: 8 ft on center
  4. 4 Gates: 2 (each replaces one section)
  5. 5 Posts: (150 ÷ 8) + 1 + 2 gate posts = 23 posts
  6. 6 Sections: 23 − 1 − 2 gates = 18 fence sections + 2 gate openings
  7. 7 Rails per section: 3 (top, middle, bottom for 6 ft fence)
  8. 8 Total rails: 18 × 3 = 54 rails
  9. 9 Pickets per section (privacy, 3.5″ wide): 96″ ÷ 3.5 = ~28 pickets
  10. 10 Total pickets: 18 × 28 + 15% waste = ~555 pickets (after rounding and waste)
  11. 11 Concrete: 2 bags (80-lb) per post × 23 posts = 46 bags
Order 23 posts, 54 rails, 555 pickets, and 46 bags of 80-lb concrete for a complete 150 ft privacy fence with 2 gates.

How Fence Materials Are Calculated

Posts: Total fence length divided by post spacing, plus 1 for the end post. Add extra posts for each gate (one hinge post and one latch post per gate). Corner posts are counted automatically where the fence changes direction.

Rails: Each section between posts gets 2 rails for fences 4 ft and under, or 3 rails for fences over 4 ft. Total rails = number of sections × rails per section.

Pickets: Section width divided by picket width (for privacy) or picket width plus gap (for spaced). Multiply by the number of sections and add your waste percentage for cuts and defects.

Concrete: Each post hole needs concrete to secure the post. The calculator estimates bags per post based on hole diameter and depth (typically 1/3 of total post length buried underground).

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Important Building Notes

Bury 1/3 of the total post length below ground. For a 6 ft fence, use 9 ft posts with 3 ft buried. For a 4 ft fence, use 6 ft posts with 2 ft buried. This rule of thirds ensures the post can resist the lateral force of wind pushing against the fence.

Let concrete cure before attaching rails. Fast-setting concrete is firm in 20–40 minutes and strong enough for rails after 4 hours. Standard concrete should cure for at least 24–48 hours before you stress the posts by nailing or screwing rails and pickets.

Rails should not touch the ground. Keep the bottom rail at least 2 inches above grade to prevent rot and allow water to drain. If ground clearance varies along the fence line, adjust picket height rather than dropping the rail into the dirt.

Crown the top of each post or add a post cap. A flat-cut post top collects water and accelerates rot. Either cut the top at a slight angle (crown cut) so water runs off, or install a post cap. Both methods significantly extend the life of your fence posts.

Frequently Asked Questions

What is the best post spacing for a wood fence? +
The standard spacing is 8 feet on center for most residential wood fences. This works well with standard lumber lengths (16 ft rails cut in half) and provides adequate strength for fences up to 6 feet tall. For fences over 6 feet or in high-wind areas, reduce spacing to 6 feet for extra rigidity.
What is the difference between a privacy fence and a spaced picket fence? +
A privacy fence has pickets installed edge-to-edge with no gaps, creating a solid visual and physical barrier. A spaced picket fence has gaps (typically 1.5-3 inches) between pickets, allowing airflow and partial visibility. Privacy fences use more pickets per linear foot and are more affected by wind loads, so post footings should be larger.
Do I need a third rail on a 6-foot fence? +
Yes. A 6-foot tall fence should have three horizontal rails: one at the top (6 inches from the top), one at the bottom (6 inches from the bottom), and one in the middle. Two rails are sufficient for fences 4 feet and under. The middle rail prevents pickets from bowing and adds wind resistance.
How do I build a fence on a slope? +
There are two methods: stepping and racking. Stepping keeps each section level and creates a stair-step pattern at the top — best for steep slopes. Racking angles each section to follow the grade for a smooth top line — best for gentle slopes. Stepped fences are easier to build but leave gaps at the bottom that may need fill boards.
Do I need a permit to build a fence? +
Most municipalities require a permit for fences over 6 feet tall, and many require one for any permanent fence. You may also need to observe setback requirements (distance from property lines and sidewalks) and height limits. Always check local codes and call 811 to mark underground utilities before digging post holes.

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Disclaimer: This calculator provides estimates for planning purposes only. Actual material requirements depend on site conditions, compaction, grading, and local building codes. Always verify measurements on-site and consult with your material supplier before purchasing.
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