Enter the length of your fence and how far apart the posts go. You get the number of posts, rails and pickets, or panels, plus how many bags of concrete to set every post.
Concrete fills each hole to 3 in below ground: 22.8 L (0.8 ft³) per post.
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This fence calculator is for homeowners and fencing crews planning a wood picket, privacy or panel fence. It counts the posts and sections from the fence length and spacing, adds rails and pickets with a small spare, and works out the concrete needed for each post hole from the hole size and your bag’s yield.
How Do You Calculate Fence Posts and Materials?
Divide the fence length by the post spacing, round up to get the sections, and add 1 for the posts. A 100 ft fence with posts 8 ft apart has 13 sections and 14 posts. With 3 rails per section that is 39 rails, and 3.5 inch pickets with 0.5 inch gaps need 315 pickets with 5% spare.
What Is the Formula for Fence Posts?
The fence post formula is posts = fence length ÷ post spacing, rounded up, plus 1 for the end post.
posts = sections + 1 + extra corner or gate posts
rails = sections × rails per section
pickets = fence length (in) ÷ (picket width + gap) × 1.05
Each straight run needs its own end post, so add one extra post for each corner and two for each gate opening. The rail is the horizontal board that runs between posts, and the picket is the upright board nailed to the rails. A panel, or prebuilt fence section, already has its rails and boards attached, so you only need posts and panels. Use the actual picket width: a nominal 1 × 4 is about 3.5 inches wide.
How Far Apart Should Fence Posts Be?
Wood fence posts are usually set 6 to 8 feet apart, and never more than about 8 feet for a standard wood fence.
| Fence type | Typical post spacing | Posts for 100 ft |
|---|---|---|
| Wood picket or privacy | 8 ft (2.4 m) | 14 |
| Wood privacy in high wind | 6 ft (1.8 m) | 18 |
| US vinyl or wood panels | 6 or 8 ft panel width | 18 or 14 |
| UK closeboard or lap panels | 1.83 m (6 ft) panel width | 18 |
| Chain link | up to 10 ft (3 m) | 11 |
Closer posts make a stronger fence in windy or soft ground. Many cities set a maximum fence height and ask for a permit, so check your local rules and property line before you dig. To total several runs of fence, the feet to meters converter helps when plans and materials use different units.
How Many Bags of Concrete Do I Need per Fence Post?
A typical 4 × 4 post in a 10 inch hole 2 feet deep needs about 2 bags of 50 lb fast setting concrete. Quikrete’s data sheet says two 50 lb bags set a 4 inch post in a 10 inch hole 2 ft deep, and each bag yields about 0.375 ft³ (11 L). The common rules are a hole about 3 times the post width and a depth of about one third to one half of the post’s height above ground, and deeper than the frost line in cold climates so frost heave does not lift the post. This tool works out the hole volume, takes away the post, and leaves the top 3 inches for soil or a sloped cap. For larger amounts, such as a long run of posts, the concrete calculator compares bags with ready mix.
How Many Pickets Do I Need for My Fence?
Divide the fence length in inches by the picket width plus the gap. For a 100 ft fence with 3.5 inch pickets and 0.5 inch gaps, 1,200 ÷ 4 = 300 pickets, or 315 with 5% spare for splits and bad boards. A privacy fence with no gap and 5.5 inch boards needs 219 boards, or 230 with spare.
Worked Example
Sam is fencing a 100 ft straight boundary with posts 8 ft apart, 3 rails per section and 3.5 inch pickets with 0.5 inch gaps. The tool shows 14 posts over 13 sections, 39 rails and 315 pickets. Each 10 inch hole, 24 inches deep, around a 3.5 inch post holds 22.8 L of concrete, which is 2.1 bags of 50 lb mix, so Sam buys 31 bags. Using 80 lb bags at 0.6 ft³ each, that drops to 19 bags. A metric run of 18 m with 1.83 m panels needs 11 posts and 10 panels.
How Do You Use the Fence Calculator?
Pick units and type
Tap Feet, inches or Meters, mm, then Pickets and rails or Panels.
Enter length and spacing
Type the fence length, post spacing or panel width, and any extra corner or gate posts.
Read the post count
Fill in rails, pickets and hole size. The big number is how many posts to buy.
Check materials
The boxes show rails or panels, pickets, and concrete bags per post and in total.
Frequently Asked Questions
How many posts do I need for a 100 ft fence?
With posts 8 ft apart, a straight 100 ft fence needs 14 posts. With 6 ft spacing it needs 18 posts. Add one post for every corner and two for every gate, since each run needs its own end posts.
How deep should fence posts be?
A common rule is to bury about one third of the post's total length, or at least half of the height above ground. A 6 ft fence usually needs holes about 2 to 3 ft deep, and deeper than the frost line where the ground freezes.
How many bags of concrete per fence post?
Most 4 × 4 posts in a 10 inch hole 2 ft deep need about 2 bags of 50 lb concrete. This tool works out the exact amount from your hole size, post size and bag yield. Bigger holes or 6 × 6 posts need more.
How many rails does a fence need?
Fences up to about 4 ft high usually need 2 rails per section. Fences 5 to 6 ft high usually use 3 rails, and taller fences may need 4. A 100 ft fence with 13 sections and 3 rails needs 39 rails.
Should fence posts be set in concrete?
Concrete is the most common choice and gives the stiffest post. Some builders use packed gravel instead so water drains away from the wood. Either way, slope the top away from the post so water does not pool against it.
What size fence panels are standard?
In the US, wood and vinyl panels are usually 6 or 8 ft wide. In the UK, standard fence panels are 1.83 m (6 ft) wide, in heights from about 0.9 to 1.8 m. Set the post spacing to the panel width plus the post.
Sources and Further Reading
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Last reviewed: October 2026