Fence Panel and Post Calculator

This calculator works out how many fence panels and posts you need for a straight fence run. You enter the total fence length, the panel width, and the post spacing, and it returns the number of panels, posts, and the total post spacing layout. It also accounts for the fact that you need one more post than panels, plus an end post at each corner.

Formula

The core calculation is simple division, but the real-world result depends on how you interpret the numbers. The calculator uses two separate formulas:

• Panels: ceil(length / panel_width) — divide the total fence length by the width of one panel, then round up to the nearest whole panel.
• Posts: ceil(length / post_spacing) + 1 — divide the length by the desired spacing between posts, round up, then add one for the end post.

Where:

• length = total fence run length (ft or m)
• panel_width = width of one pre-made panel (ft or m)
• post_spacing = distance between post centers (ft or m)

The ceil() function means you always round up — you can’t buy a third of a panel or a fraction of a post. The +1 for posts is the most commonly missed step: a 100 ft run with posts every 8 ft needs 13 posts, not 12, because the last post closes the run.

Worked Example

Using the default values from the calculator:

• Fence length = 100 ft
• Panel width = 6 ft
• Post spacing = 8 ft

Panels: 100 ÷ 6 = 16.67 → round up to 17 panels

Posts: 100 ÷ 8 = 12.5 → round up to 13, then add 1 = 14 posts

So for a 100 ft fence with 6 ft panels and 8 ft post spacing, you need 17 panels and 14 posts. The calculator gives exactly that: 17 and 14.

Notice the panels and posts don’t line up perfectly — 17 panels at 6 ft each covers 102 ft, which is slightly more than 100 ft. That’s normal; you trim the last panel or adjust the spacing. The post spacing of 8 ft is an average, not a rigid grid.

How to Choose Panel Width and Post Spacing

The two numbers you enter are not independent. They should relate to the material you’re using and the wind load in your area.

• Panel width is usually fixed by what you buy — common sizes are 6 ft and 8 ft (1.8 m and 2.4 m). If you’re building a custom fence, you can choose any width, but standard sizes are cheaper.
• Post spacing is a structural decision. For a typical 6 ft high privacy fence, 8 ft spacing is common. For taller fences or high-wind areas, 6 ft spacing is safer. For a low decorative fence, 10 ft spacing may be fine.
• If you’re using pre-made panels, the post spacing should match the panel width — you don’t want a 6 ft panel between posts that are 8 ft apart.

A good rule: pick the panel width first, then set post spacing equal to that width (or slightly less if you want extra strength). The calculator lets you test different combinations before you buy.

Common Mistakes and How to Avoid Them

The biggest error is forgetting the extra end post. Another is mixing units — if you measure the fence in feet but the panel width in inches, you’ll be off by a factor of 12. Always convert everything to the same unit before dividing.

Rounding also trips people up. You can’t buy 16.67 panels, so you round up to 17. But that means you have 2 ft of extra panel material. If you’re cutting panels to fit, you might instead buy 16 panels and cut the last one, but that only works if the last panel can be trimmed without ruining it. The calculator assumes you buy whole panels and trim the last one to fit.

Another subtlety: post spacing is measured center-to-center, not edge-to-edge. If you place posts 8 ft apart from outside edge to outside edge, the actual spacing between centers is less, and you’ll need more posts than calculated.

When to Use This Calculator

This tool is for a straight fence run with evenly spaced posts and uniform panels. Use it for:

• Planning a new privacy fence around a yard
• Estimating materials for a garden boundary
• Replacing a section of an existing fence
• Comparing costs of different panel widths

It does not handle:

• Corners — each corner needs a post, and the calculator assumes a single straight line. For an L-shaped fence, run the calculation twice, once per leg, and add an extra post at the corner.
• Gates — a gate opening replaces one or more panels and needs its own posts on each side.
• Sloped ground — panels may need to be stepped or cut, which changes the number of panels.
• End posts at walls or buildings — if the fence attaches to a structure, you may not need an extra end post on that side.

For those cases, break the fence into straight segments and add the extra posts manually.

Cost and Material Considerations

The calculator gives you counts, not costs. To estimate budget, multiply the number of panels by the price per panel, and the number of posts by the price per post. Add:

• Concrete for setting posts (typically 1–2 bags per post, but check the bag coverage)
• Gravel for drainage at the base of each post
• Screws or nails for attaching panels to posts
• Post caps and concrete forms if you want a finished look

Also consider waste — if you’re cutting panels, add 5–10% extra for mistakes or damaged pieces. The calculator’s rounding already covers some waste, but not if you need to cut every panel.

Alternatives to Pre-Made Panels

If you’re not using standard panels, the calculation changes:

• Picket fence: you calculate the number of pickets (spacing + picket width) and the number of rails (usually 2–3 per section), not panels.
• Chain link: you buy rolls of fabric by length, and posts are typically 10 ft apart. The panel calculation doesn’t apply.
• Rail fence: posts are spaced 8–10 ft apart, and you buy rails by the linear foot, not panels.

For any of these, the post count formula still works: ceil(length / spacing) + 1. Only the panel part changes.

Frequently Asked Questions

Why do I need one more post than panels?

Every panel needs a post on each side. If you have 10 panels in a row, you have 11 posts — one at the start, one between each panel, and one at the end. The formula adds the +1 to account for that final post.

Can I use 8 ft panels with 6 ft post spacing?

Yes, but you’ll have 2 ft of unsupported panel between posts, which may sag or catch wind. It’s better to match spacing to panel width, or use a shorter panel. The calculator will give you more posts than panels, which is wasteful.

What if my fence has a corner?

Run the calculation for each straight section separately, then add one extra post at the corner (the corner post serves both sections). For an L-shaped fence with two 50 ft legs, you’d calculate each leg as 50 ft, then add 1 extra post at the corner.

How do I account for a gate?

Subtract the gate width from the total fence length before calculating. Then add two extra posts — one on each side of the gate — to the final post count. For example, a 100 ft fence with a 4 ft gate becomes a 96 ft fence, plus 2 gate posts.

Should I round up or down?

Always round up for materials. You can’t buy half a panel, and cutting a panel shorter is easier than stretching it. Rounding up also gives you a small buffer for mistakes.

Does the calculator work in meters?

Yes, as long as you enter all three values in the same unit. The math is unit-agnostic — it just divides numbers. If you enter meters, you get panels and posts, no conversion needed.

Related

• Board Calculation Methods for Lumber Projects
• Basic Calculator for Board Exam: What You Need
• Aluminum Fence Material Calculator

in length | Fence length | ft | 100 | 0 | 10000
in panel | Panel width | ft | 6 | 1 | 20
in post | Post spacing | ft | 8 | 1 | 20
out panels | Panels needed | panels | ceil(length / panel) | 0
out posts | Posts needed | posts | ceil(length / post) + 1 | 0