How to build a fence

A fence is a simple structure that fails in predictable ways: posts set too shallow, spaced too far apart, or one post short because of an off-by-one in the counting. Get the layout and the holes right and the rest is repetition. This is the order of work, the numbers that matter, and the arithmetic — which the fence calculator will do for your run.

Before you dig

Confirm the property line. A fence built over the boundary is a legal problem, not a carpentry one. If the line is uncertain, a survey costs far less than moving a finished fence.
Check permits and rules. Height limits, setbacks and which side faces outward are commonly regulated, and an HOA may add more.
Have utilities located. Free in most places and the alternative is hitting a gas or fibre line with a post-hole digger.

Layout: spacing, and the off-by-one

Set the two end posts first, run a string line tight between them, and mark post positions along it. Spacing of 6 to 8 feet on centre is standard: 8 ft keeps the post count and cost down, 6 ft gives a stiffer fence and is worth it for tall privacy panels, which catch wind like sails.

Then the mistake that catches nearly everyone: a run has one more post than it has sections. Ten sections need eleven posts. On top of that, add one post per corner or direction change, and two per gate opening. Buying exactly one post short is the single most common fence-material error, and it always shows up at the end of the day when the yard has closed.

Post holes and concrete

Depth rule: a third of the post's above-ground height, or below the frost line — whichever is deeper. A 6 ft fence therefore wants holes around 2 ft deep, more in cold regions. Frost heave is what wrecks shallow-set fences; water freezes, expands, and lifts each post a fraction every winter until the line visibly waves.

For a 4×4 post in an 8-inch hole at 2 ft deep, budget two 50 lb bags of fast-setting concrete per post. Gate and corner posts take three or more — they carry leverage the line posts do not. Set the post plumb, brace it in two directions, and crown the concrete slightly above grade so water sheds away from the timber rather than pooling around it. Bag yields vary by brand: check the stated yield against your hole volume, and if you are pouring rather than using fast-set, thecubic feet calculator converts hole dimensions to volume.

Worked example: a 100 ft privacy fence

A straight 100 ft run at 8 ft spacing, three rails per section, 5½ in boards butted tight:

Sections: 100 ÷ 8, rounded up = 13
Posts: 13 + 1 = 14 (plus one per corner, two per gate)
Rails: 13 × 3 = 39
Pickets: (100 × 12) ÷ 5.5, rounded up = 219
Concrete: 14 × 2 = 28 × 50 lb bags, more for gate posts

Those are the counts the fence calculatorproduces for the same inputs — it computes them with the same tested module that generated the figures on this page, so the two cannot disagree. Add a waste allowance on pickets: they warp, split and get cut.

Order of work

Mark the line, set end and corner posts, string a line between them.
Mark and dig every hole to depth; add gravel to the base for drainage.
Set posts plumb in concrete, braced, working to the string line. Let them cure before hanging anything on them.
Cut posts to a consistent height after setting — much easier than trying to set each one at exactly the right height.
Fix rails, then pickets or panels, checking level every few boards rather than at the end.
Hang gates last, on the deepest-set posts.

Why we don't quote a price per foot

The most-searched fence question is what one costs per foot, and the honest answer is that the figure is mostly labour and varies too much by region, terrain and contractor for a single number to mean anything. What is exact is the material list — posts, rails, pickets, panels, concrete — which the calculator gives you. Price that list locally, and take separate labour quotes if you are not building it yourself. A materials count you can trust beats a national average price you cannot.

Frequently asked questions

How much concrete per fence post?

For a 4×4 post in an 8-inch-wide hole dug 2 feet deep, roughly two 50 lb bags of fast-setting mix per post is the common working figure. Gate posts and corner posts take more — three or more bags — because they are levered hard and usually set deeper. Bag yields differ by brand, so check the stated yield on the bag against your actual hole volume rather than assuming.

How deep should fence posts go?

The usual rule is a third of the post’s above-ground height, or below the local frost line, whichever is deeper — so a 6 ft fence typically wants holes about 2 ft deep, and colder regions want more. Frost heave is what destroys shallow-set fences: water in the soil freezes, expands and lifts the post a little each winter until the line goes crooked.

How far apart should fence posts be?

6 to 8 feet on centre is standard. Eight feet suits most panel and picket fences and keeps the post count down; six feet gives a stiffer fence and is worth it in windy spots or for heavy privacy panels, which act like sails. Whatever spacing you pick, the post count is always one more than the number of sections — the off-by-one that catches everyone.

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

At 8 ft spacing, a 100 ft straight run divides into 13 sections and therefore needs 14 posts — not 13. Add one more post for every corner and every direction change, and two per gate. Our fence calculator does the section-and-post arithmetic and the concrete bags in one go.

Should I set fence posts in concrete or gravel?

Concrete gives the most rigid setting and is standard for gate posts and anything carrying load. Compacted gravel drains better and lets a post be replaced without excavating a concrete plug, which suits wet ground and rot-prone timber. A common compromise is gravel in the base of the hole for drainage with concrete above, so the post foot is never standing in water.

Do I need a permit to build a fence?

Often yes, and it varies by locality — height limits, setback from the boundary, and rules about which side faces out are all commonly regulated, and a homeowners’ association may add its own. Two things worth doing before you dig regardless: confirm your property line, and have underground utilities located. Hitting a buried service is expensive and dangerous.

What does a fence cost to build?

We deliberately do not publish an installed price per foot — that figure is mostly labour and varies enormously by region, terrain and contractor, so any single number would be misleading. What we can give you exactly is the material count: posts, rails, pickets or panels and concrete bags. Price that list at your local yard, and get quotes for labour separately if you are not building it yourself.

About these numbers

The counting arithmetic on this page is computed by the same tested module thefence calculator uses, so the worked example always matches the tool — read how CubicMath works. The spacing, depth and concrete figures are standard trade practice rather than a single manufacturer's spec, and are described as rules of thumb for that reason; your local code and your concrete bag's stated yield both outrank them. Setting posts in a new gravel drive at the same time? Thegravel calculator handles that layer.