Fence Calculator
Count posts, rails and pickets for a wood fence of any length.
What you'll need to order
- 4x4 posts
- 2x4 rails
- fence pickets
- fast-setting concrete
- exterior screws
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
posts = (length ÷ spacing) + 1 · pickets = length × 12 ÷ picket width
This assumes butted pickets with no gap. For a spaced picket fence, add your intended gap to the picket width before dividing. Corner and gate posts should be 6x6 rather than 4x4.
Worked example
With fence length 100 ft, post spacing 8 ft, picket width 5.5 in, rails per section 3 , this calculator returns 13.5 .
Fence posts by spacing
Figures below assume fence length 100 ft × picket width 5.5 in × rails per section 3 . Change any measurement in the calculator to get your own numbers.
| Post spacing | Posts needed | Rail material (ft) |
|---|---|---|
| 4 ft | 26.00 | 300.0 |
| 6 ft | 17.67 | 300.0 |
| 8 ft | 13.50 | 300.0 |
| 10 ft | 11.00 | 300.0 |
| 12 ft | 9.33 | 300.0 |
Per 100 linear feet. Closer spacing costs more in posts and concrete but produces a noticeably stiffer fence, which matters most on exposed or windy sites.
Materials for common fence runs
| Job | Size | Posts needed |
|---|---|---|
| Front garden, 3 ft picket | 60 ft × 6 ft × 3.5 in × 2 | 11.00 |
| Side return | 40 ft × 8 ft × 5.5 in × 3 | 6.00 |
| Typical back garden | 150 ft × 8 ft × 5.5 in × 3 | 19.75 |
| Quarter-acre perimeter | 420 ft × 8 ft × 5.5 in × 3 | 53.50 |
| Paddock rail fence | 500 ft × 10 ft × 6 in × 3 | 51.00 |
Add one post for every corner and every gate side. The calculation gives the run itself, not the extra posts a shape with corners needs.
What does a fence cost per foot?
Material typically runs $18 to $60 per linear foot installed. Pressure-treated wood sits at the bottom of that range, cedar and vinyl at the top. Materials alone are typically 40 to 50% of the installed figure.
What moves the price:
- Material — treated pine, cedar, vinyl and composite span a three-fold range
- Height: a 6 ft fence uses far more than twice the material of a 3 ft one
- Ground conditions, since rock or heavy clay slows post holes considerably
- Slope, which forces either stepped or racked panels
- Gates, at $200 to $600 each
Prices are US averages and move with fuel, season and haul distance. Always get two local quotes before budgeting.
Post depth by fence height
| Type | Post hole depth (in) | Notes |
|---|---|---|
| 3 ft picket fence | 24.00 | Or one third of post length |
| 4 ft fence | 24.00 | Below the frost line in cold climates |
| 6 ft privacy fence | 30.00 | The usual residential case |
| 8 ft fence or windy site | 36.00 | Wind load rises sharply with height |
| Gate posts, any height | 42.00 | Gates work the post constantly |
The rule of thumb is one third of the post length in the ground, or below the local frost line — whichever is deeper. A post that heaves in the first winter takes the whole fence with it.
Frequently asked questions
How many fence posts do I need for 100 feet?
Fourteen at 8 ft spacing, including both end posts. Add one more for every corner and one for each side of a gate.
How much does a fence cost per foot?
Treated wood runs $18 to $30 per linear foot installed, cedar $30 to $45 and vinyl $35 to $60. A 150 ft back garden fence therefore lands between $2,700 and $9,000.
How much fence can I build in a day?
A two-person crew sets 15 to 20 posts a day, then hangs rails and pickets on a second pass. Posts need 24 to 48 hours for the concrete to cure before anything is fixed to them.
Which side of the fence faces the neighbour?
Convention puts the finished side outward, facing the neighbour or the street, with rails and posts on your side. Some local ordinances and HOA rules make this a requirement rather than a courtesy.
How far apart should fence posts be?
Eight feet on centre for a standard wood fence, dropping to six where wind loads are high or the fence is a solid privacy design. Wider than eight and the rails sag between posts.
How many pickets do I need per foot of fence?
With 1x6 pickets butted tight, about 2.2 per foot. With 1x4 pickets it is 3.4 per foot. Add your gap width to the picket width first if you are building a spaced fence.
How deep should fence posts be set?
A third of the total post length, or below the frost line, whichever is deeper. A 6 ft fence needs an 8 ft post set 24 to 30 inches deep in mild climates.
Should fence rails be two or three?
Two rails suit fences up to 4 ft. Six-foot privacy fences need three, and the middle rail is what stops the pickets cupping and twisting over time.