Fence Calculator

Enter your fence length, post spacing and gates to estimate posts, rails, pickets or boards, and concrete bags. Works in US units or metric.

How the fence calculator works

1. Fence run: total length minus the width of any gates.
2. Sections: fence run ÷ post spacing, rounded up.
3. Posts: one more post than sections, plus one extra post for each gate, because a gate breaks the run.
4. Rails: sections × rails per section.
5. Pickets or boards: fence run ÷ (board width + gap), rounded up.
6. Concrete: posts × bags per post.

Example: 100 ft of privacy fence with one 4 ft gate

• Fence run: 100 − 4 = 96 ft
• Sections at 8 ft spacing: 96 ÷ 8 = 12
• Posts: 12 + 1 + 1 for the gate = 14
• Rails (3 per section): 36
• Boards (5.5 in wide, no gap): 96 × 12 ÷ 5.5 = 209.5, so 210
• Concrete at 2 bags per post: 28 bags

This is a simple straight-line estimate. Corners, slopes and gate hardware can change the numbers, so draw your fence line and count corner posts separately.

Fence planning tips

• Call before you dig. In the US, call 811 a few days before digging post holes so underground lines can be marked.
• Check the rules. Many towns and homeowners associations limit fence height and style, and some require a permit. Confirm your property line before you build.
• Post spacing. 6–8 ft between posts is common for wood fences. Closer spacing is stronger, especially in windy areas.
• Post depth. A common rule of thumb is to set posts at least one-third of their above-ground height into the ground (about 2 ft or more for a 6 ft fence), and deeper where the ground freezes. Follow local code.
• Concrete. Bags per post depend on hole size and bag weight. Check the bag’s coverage chart and adjust the calculator.
• Buy a few spares. Some boards will be warped or split, so add 5–10% extra.

Frequently asked questions

How many posts do I need for a 100 ft fence?

With posts every 8 ft and no gates, 100 ft needs 13 sections and 14 posts. Each gate adds about one more post.

How many pickets do I need per foot?

Divide 12 inches by the picket width plus the gap. With 3.5 in pickets and a 2 in gap, that is about 2.2 pickets per foot.

Does this work in metres?

Yes. Switch to metric and enter the length and spacing in metres and the board width and gap in millimetres.