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Privacy Dog Ear Fence Calculator
Work out posts, rails, pickets, concrete and fasteners for a privacy fence with no gaps between pickets.
Your result
Enter your numbers and press the button. Your result appears here.
Calculation Formula
Posts
\[\text{Number of Posts} = \left\lceil \frac{\text{Fence Length (ft)}}{\text{Post Spacing (ft)}} \right\rceil + 1\]
Rails
\[\text{Total Number of Rails} = (\text{Number of Posts} - 1) \times \text{Number of Rails}\]
Pickets
\[\text{Number of Pickets} = \left\lceil \frac{\text{Fence Length (ft)} \times 12}{\text{Picket Width (in)}} \right\rceil\]
Concrete
\[\text{Bags per Post} = \left\lceil \frac{\left(\pi \left(\frac{D}{2}\right)^2 - w^2\right) \times d \div 1728}{0.375} \right\rceil\]
Fasteners
\[\text{Picket Fasteners} = \text{Number of Pickets} \times \text{Number of Rails} \times 2\]
D is the hole diameter (3 × the post width), w is the actual post width (3½ in for a 4×4), d is the depth of concrete in inches and 0.375 ft³ is the yield of a 50 lb bag of fast-setting concrete. Posts go in the ground half as deep as the fence is tall, with 6 in of gravel underneath.
Example: 100 ft of fence needs 14 posts, 39 rails, 219 pickets and 70 bags of fast-setting concrete.
Rules of thumb
| Item | Typical |
|---|---|
| Depth in the ground | ⅓ of the post length, or below the frost line |
| Hole width | About 3 × the post width |
| Wood post spacing | 6 to 8 ft |
| Chain link line posts | No more than 10 ft |
| T-posts for barbed wire | 8 to 12 ft |
| Field fence | Wood posts 8–10 ft, T-posts 6–8 ft |
Common questions
How many rails does a fence need?
Two rails for fences up to about 4 ft, three for 5 to 6 ft and four for 8 ft fences.
Should posts be 4×4 or 6×6?
4×4 posts are standard for fences up to 6 ft. Use 6×6 for 8 ft fences, gate posts and windy sites.
How long should fence posts be?
Height above ground plus the depth in the ground. For a 6 ft fence that is usually a 9 ft post, so buy 10 ft stock and cut it, or set 8 ft posts deeper only where frost and soil allow.
How many pickets are in an 8 ft section?
With 5½ in pickets butted together, 96 ÷ 5.5 = 17.5, so 18 pickets. With 3½ in pickets and 2½ in gaps, 17.
Sources
- Quikrete, Concrete Mix data sheet (bag yields): https://www.quikrete.com/PDFs/DATA_SHEET-Concrete%20Mix%201101.pdf
- Quikrete, project calculator (post depth example): https://www.quikrete.com/calculator/