Fence Calculator
Calculate fence materials including posts, rails, pickets, and concrete needed for your project. See also Deck Calculator, Concrete Calculator, and Board Foot Calculator.
Cost Estimate (optional)
How to Use the Fence Calculator
Enter your total fence length in linear feet, the desired height, and post spacing (typically 6 to 8 feet on center). Select 2 or 3 rails depending on fence height — fences over 5 feet generally require 3 rails for stability. Specify picket width (standard is 3.5 inches for a 1x4 board) and the gap between pickets (0 for a privacy fence, 1-2 inches for a semi-private style). The calculator determines the number of posts, rails, pickets, total board feet of lumber, and bags of concrete needed to set posts.
Formula
Posts = (Fence Length / Post Spacing) + 1
Rails = (Posts - 1) x Rails per Section
Pickets = Fence Length / ((Picket Width + Gap) / 12)
Concrete Bags = Posts x 2 (50 lb bags per post)
Example Calculation
Fence: 100 ft long, 6 ft tall, 8 ft post spacing, 3 rails
Posts = (100 / 8) + 1 = 13.5 → 14 posts
Rails = 13 sections x 3 = 39 rails
Pickets = 100 / (3.5 / 12) = 343 pickets
Concrete = 14 posts x 2 bags = 28 bags (50 lb)
Reference Table
| Fence Height | Post Length | Rails | Post Depth | Common Use |
|---|---|---|---|---|
| 4 ft | 6 ft | 2 | 24 in | Decorative / garden |
| 5 ft | 7 ft | 2-3 | 24 in | Property line |
| 6 ft | 8 ft | 3 | 24-30 in | Privacy fence |
| 8 ft | 10 ft | 3 | 30-36 in | Security / wind |
Frequently Asked Questions
How deep should fence posts be set?
Fence posts should be buried at least 1/3 of their total length. For a 6-foot fence with an 8-foot post, bury 24-30 inches deep. In areas with frost, posts should extend below the frost line to prevent heaving.
How much concrete per fence post?
Each fence post typically requires 1-2 bags of 50 lb concrete mix depending on hole diameter. A standard 10-inch diameter hole that is 24 inches deep needs about 1.5 bags. Larger 12-inch holes need 2 bags per post.
What is the best post spacing for a fence?
Standard post spacing is 6 to 8 feet on center. Use 6-foot spacing for taller fences (over 6 ft) or high-wind areas. 8-foot spacing works well for standard 6-foot privacy fences in moderate climates and keeps material costs lower.
Should I use 2 or 3 rails?
Use 2 rails for fences 4 feet or shorter. Fences 5-6 feet tall should have 3 rails for adequate support. Three rails prevent pickets from warping and provide better wind resistance for privacy fences.
How long does a wood fence last?
Pressure-treated pine fences last 15-20 years. Cedar fences last 15-25 years due to natural rot resistance. Redwood can last 20-30 years. Proper maintenance including staining every 2-3 years extends lifespan significantly.
What size lumber is used for fence rails?
Standard fence rails are 2x4 lumber (actual 1.5 x 3.5 inches) cut to the post spacing length, typically 8 feet. For heavy-duty fences or spans over 8 feet, 2x6 rails provide additional strength and rigidity.