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)
Related Calculators:
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.