Split Rail Fence Calculator
Calculate how many posts you need for a rustic split rail fence at 10 ft spacing, based on your fenced area's perimeter, plus total cost.
How this calculator works
This calculator treats your fenced area as a rectangle: it computes the perimeter from the two side lengths you enter, divides by the standard 10 ft split rail post spacing, and adds one post to close the loop.
Formula: Perimeter = 2 × (Length + Width). Posts = floor(Perimeter ÷ Spacing) + 1.
Worked example
A fenced area 100 ft x 50 ft, with posts spaced 10 ft apart:
- Perimeter: 2 × (100 + 50) = 300 ft
- Posts: floor(300 ÷ 10) + 1 = floor(30) + 1 = 31 posts
- At $20/post, that’s 31 × 20 = $620.00.
Coverage reference
| Perimeter | Posts needed (10 ft spacing) |
|---|---|
| 200 ft | 21 posts |
| 300 ft | 31 posts |
| 500 ft | 51 posts |
How to measure your fence line
Measure the two distinct side lengths of your rectangular, fully enclosed fence run. Once you have the post count, multiply the number of sections (posts minus one) by your rail count per section — 2 for a standard 2-rail fence, 3 for a taller 3-rail fence — to get total rails.
Frequently asked questions
How far apart are split rail fence posts spaced?
10 ft is standard, matching the common 10 or 11 ft length of split rail sections sold at most lumber yards. Rails typically overlap slightly into a mortise hole in the post, so the post-to-post distance stays close to 10 ft even though the rail itself is a bit longer.
How many rails do I need per section?
That depends on whether you're building a 2-rail or 3-rail fence. Multiply the number of sections (posts minus one) by your rail count per section — a 2-rail fence uses 2 rails per gap between posts, a 3-rail fence uses 3. This calculator gives post count only; rail count is a separate multiplication based on your chosen style.
Do split rail posts need concrete?
Not always — split rail is a lightweight, low-wind-load fence style, so many installers simply tamp the post into a dug hole with compacted soil or gravel rather than pouring concrete. Concrete does add stability in loose or sandy soil, or if you want extra long-term rigidity.
Why is 2-rail vs. 3-rail split rail mostly decorative?
Split rail is a low-security, decorative or boundary-marking fence rather than a containment fence — it doesn't stop most pets or wildlife. 3-rail adds a bit more visual height and a slightly more finished look, but the structural spacing and post count are identical to 2-rail.
Why isn't waste included for split rail posts?
Posts are set at a fixed count determined by your perimeter and spacing, with every post going into the ground — there's no cutting or offcut waste the way there is with rails or panel material.
Estimates only. Verify quantities with your supplier before purchasing.