How Much Fencing Do I Need?

A fence estimate is really three estimates: how many posts hold it up, what fills the space between them, and how much concrete sets the posts. All three come from one measurement, the length of the fence line, plus a few decisions about post spacing, gates, and fence style.

Step 1: Measure the fence line

Measure each straight side separately, in feet, along the line where the posts will stand. Note which sides connect at a corner, where each gate goes, and how wide each gate opening is, measured post to post.

Before measuring for real, confirm where your property line is. A survey or your property plat is more reliable than an old fence. Many towns also limit fence height, often to around 6 ft in back yards and lower in front yards, and HOAs can add their own rules. Check both before you buy anything.

Step 2: Choose post spacing and count sections

Posts are usually set 6 to 8 ft apart, center to center. For prebuilt panels, the spacing is fixed by the panel width, commonly 8 ft for wood privacy panels. For a fence built from pickets and rails, 8 ft spacing is common because it suits standard 8 ft rails.

Sections per side = side length ÷ post spacing, rounded up

Round up on every side, since a short leftover still needs its own section and its own post. For a backyard with sides of 60, 100, and 60 ft at 8 ft spacing:

Step 3: Count the posts

How the sides connect changes the count:

• One continuous line (corners shared, open at both ends): posts = sections + 1.
• A closed loop (fully enclosed, ending where it started): posts = sections.
• Separate runs that do not touch: each run needs its own end post, so posts = sections + 1 for every run.

Then add one post for each gate, so both sides of the opening have a post. The example is one continuous line: 29 + 1 = 30 posts, plus 1 for the gate, gives 31 posts.

Gate posts carry more load than line posts, so they are often a larger size, such as 6 × 6 instead of 4 × 4, or set deeper. Follow the gate manufacturer’s recommendation.

Step 4: Count what goes between the posts

Prebuilt panels

Buy one panel for each section. The example has 29 sections, so about 29 panels of 8 ft. Sections that come out shorter, at the end of a side or next to the gate, take a panel cut to length, so you still need a full panel for each.

Pickets and rails

For a board-by-board fence, rails run between posts: usually 2 rails for fences up to about 4 ft, and 3 rails for 6 ft privacy fences. Rails = sections × rails per section, so 29 × 3 = 87 rails in the example.

Pickets cover the length of the fence minus the gate openings. Use the actual picket width: a nominal 1 × 6 picket is 5.5 in wide.

Pickets = length to fill (in) ÷ (picket width + gap), rounded up

The example has 220 − 4 = 216 ft to fill, which is 2,592 in:

An extra 5 to 10% covers split, warped, and cut-to-fit boards. Pick through the stack at the store if you can, and set the worst boards aside for cuts.

Step 5: Post concrete

Each post hole needs concrete equal to the hole volume minus the part of the post inside it. Holes are commonly about three times the post width in diameter and deep enough to bury about a third of the post, and below the frost line in cold climates. Your local code and the post manufacturer set the actual requirement.

For a 4 × 4 post in a 10 in hole, 3 ft deep, each hole needs about 1.38 cubic feet of concrete. For 31 posts, that is about 42.8 cubic feet, or 72 bags of 80 lb concrete at a typical 0.60 cu ft yield. Our concrete bags guide walks through this calculation in detail.

Before you dig

• Call 811. In the U.S., contact 811 a few business days before digging so underground utility lines can be marked. It is free, and in many states it is required.
• Confirm the line and permits. Many towns require a permit, a setback from the property line, or a specific finished side facing out.
• Buy matching hardware. Count gate hinges and latches, and fasteners for rails and pickets. Use exterior-rated fasteners for pressure-treated lumber.
• Check the actual product sizes. Panel widths, post sizes, and rail lengths vary by product, and your counts should use the real numbers.

Frequently asked questions