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- A 100 ft fence with one 4 ft gate and 8 ft panels needs 12 panels and 14 posts.
- Two 50 lb bags of concrete per post means 28 bags.
- As a picket fence with 5.5 in pickets and 1/2 in gaps, it needs about 202 pickets and 36 rails.
- Post length is the fence height plus about 2 ft for burying.
How to use the fence calculator
Enter the total fence length
Measure the full line, including the space where gates will go.
Pick the height and style
Choose ready-made panels or pickets and rails, and select the fence height.
Set post spacing and gates
Match post spacing to your panel width. Each gate removes its width from the fence line and adds one post.
Check concrete and waste
Set bags of concrete per post, and for pickets add a waste allowance.
How the fence materials are calculated
Fence formulas
Fence run = total length − gates × gate width
Sections = fence run ÷ post spacing, rounded up
Posts = sections + 1 + gates
Pickets = run in inches ÷ (picket width + gap) × (1 + waste %)
Concrete bags = posts × bags per post
Rails are 2 per section for fences under 6 ft and 3 per section for 6 ft and taller in this calculator.
Worked example: a 100 ft, 6 ft tall fence
The fence has one 4 ft gate, posts every 8 ft and 2 bags of concrete per post.
- Fence run (100 − 4) 96 ft
- Sections (96 ÷ 8) 12
- Posts (12 + 1 + 1) 14
- Post length (6 + 2) 8 ft
- Concrete bags (14 × 2) 28
- Pickets (96 × 12 ÷ 6.0 × 1.05) 202
- Rails (12 × 3) 36
With ready-made panels, you need 12 panels. With pickets and rails, you need 202 pickets and 36 rails instead.
Fence calculator FAQ
How many fence posts do I need?
Divide the fence run by the post spacing to get the sections, then add one post for the end and one for each gate.
How do I calculate the number of pickets?
Divide the fence run in inches by the picket width plus the gap, then add a waste allowance.
How many bags of concrete per post?
Many installers use one to two 50 lb bags per post. Soil, post size and local climate change the amount.
How long should the posts be?
About 2 feet of the post is buried in many cases, so add 2 ft to the fence height. Frost depth in cold regions may require more.
How many rails are in each section?
Two rails are typical for shorter fences and three for 6 ft or taller. Check your design.
Do gates change the count?
Yes. A gate takes up part of the fence line and needs its own extra post, which the calculator accounts for.