Split Rail Fence Calculator
A split rail fence calculator divides the perimeter by post spacing: a 100 × 50 ft enclosure with posts every 10 ft needs 30 posts, or $600 at $20 each.
Split rail fence calculator formula
A split rail fence calculator finds the number of posts needed to go around an enclosure. Perimeter = 2 × (length + width). Posts = perimeter ÷ post spacing, rounded up. This tool treats the fence as a closed loop, so there is no extra post at the end. The cost is posts × price per post, with $20 as the default.
The formula in plain words
Walk around the whole fence line and add up the feet. Divide the total by how far apart the posts are. Round up to a whole post. In a closed loop, every section ends at a post and the last section meets the first post, so posts equal sections.
Worked examples
These match the calculator exactly.
- Paddock: 100 ft × 50 ft, posts every 10 ft, $20 per post
- Perimeter: 2 × (100 + 50) = 300 ft
- Posts: 300 ÷ 10 = 30
- Cost: 30 × $20 = $600
- Garden enclosure: 60 ft × 40 ft, posts every 8 ft, $20 per post
- Perimeter: 2 × (60 + 40) = 200 ft
- Posts: 200 ÷ 8 = 25
- Cost: 25 × $20 = $500
- An open front boundary of 100 ft, posts every 10 ft
- Enter length 50 and width 0, which gives a 100 ft perimeter
- Tool result: 10 posts
- Add 1 for the end post: 11 posts
Rails, sections and spacing
| Item | How to count it |
|---|---|
| Posts | Perimeter ÷ spacing, from the tool |
| Sections | The same as posts for a loop, posts minus 1 for a line |
| Rails | Sections × rails per section |
| Gates | Count separately, each replaces a section |
In example 1, 30 sections with 3 rails each is 90 rails. In example 2, 25 sections with 2 rails each is 50 rails.
Spacing and rail length
Split rails are cut to a standard length, and the posts are set to match. Rails of 10 feet go with posts 10 feet apart, and rails of 8 feet go with posts 8 feet apart, measured center to center. If you plan an odd length, shorter sections at the end can use a cut rail.
Gates and openings
A gate takes the place of one section. Gate posts carry the weight of the gate and swing, so use larger posts set deeper and tamp them well. For a 10 ft gate in example 1, you lose one 10 ft section of rails and add the gate hardware, which you price separately.
Setting the posts
Posts need to be set deep enough to stay upright. A common rule of thumb is to bury about a third of the post length, but depth also depends on frost depth and soil. Use the fence post depth calculator and your local frost depth. Tamp gravel or soil around the post as you backfill, and set corner and gate posts more firmly than the line posts. Check that gates swing freely before the concrete sets.
Before you dig, call your local utility locator service, such as 811 in the United States, so you do not hit a buried line.
How to measure
Run a string around the planned fence line and measure it. Mark post locations with stakes or paint. If the ground is uneven, measure along the ground, since rails follow the land. For a loop that is not a rectangle, add each side by hand and divide the total by the spacing, rounding up.
Property lines and rules
Before you plan the fence, find out where your property line is and whether your town has rules on fence height, material or setback. Some neighborhoods have extra rules. A fence that crosses a line can cause a dispute, so a survey is worth having if the boundary is unclear. The tool counts posts for a rectangle, but it cannot check these things.
Common mistakes
- Using the loop result for an open line. Add the end post.
- Forgetting the gate posts.
- Mixing up spacing and rail length.
- Not checking property lines or local fence rules.
- Leaving out concrete or gravel for the posts.
Related pages
For general fence posts, see the fence post calculator. For steel posts, use the t-post calculator. To set posts in concrete, see the fence post concrete calculator.
Frequently asked questions
How many posts do I need for a split rail fence?
Add up the fence length and divide by the spacing, rounding up. This tool treats the fence as a closed rectangle, so it uses the perimeter. A 100 × 50 ft enclosure has a 300 ft perimeter, and posts every 10 ft means 30 posts.
What if my fence is a straight line and not a loop?
An open line needs one more post than it has sections. The tool does not add that one. Enter half the line as the length and zero as the width, then add 1 post. A 100 ft line at 10 ft spacing is 10 sections and 11 posts.
How many rails do I need?
Count the sections and multiply by the rails per section. Most split rail fences use 2 or 3 rails. With 30 sections and 3 rails each, that is 90 rails. Check the length of the rails you buy, since that sets the post spacing.
How far apart should split rail posts be?
It depends on the rail length. Rails are commonly 8 or 10 feet long, and posts are set to match. Use the spacing printed on your product.
Does the price include rails, gates and hardware?
No. The tool prices posts only, at $20 each by default. Add rails, gates, post caps and concrete or gravel separately.
Estimates only. Verify quantities with your supplier before purchasing.