Fence Calculator

Fence Calculator: Posts, Pickets and Panels You Need

A fence is one of those jobs that looks simple until you are standing in the store trying to work out how many fence posts do I need, how many pickets will cover the run, and how much concrete will hold it all up. This page does that maths for you in imperial or metric units, shows every formula it uses, and helps you price the materials before you buy anything.

Quick answer

For a 6 ft privacy fence with posts every 8 ft, pickets 5.5 in wide and no gap between them, the materials for the most common fence lengths are below. These figures are before any waste allowance, and rails are counted at three per section because the fence is 6 ft tall.

Fence length	Posts	Rails	Pickets
50 ft	8	21	110
100 ft	14	39	219
150 ft	20	57	328
200 ft	26	75	437

A short regional note: in the UK, fence panels are a standard 6 ft (1.83 m) wide and are normally fitted between 75 mm or 100 mm posts, often with a gravel board along the bottom, and height limits apply — generally 2 m, or 1 m next to a highway in England — so always check before you build. In Australia, paling fences are commonly 1.8 m high and Colorbond panels are about 2.36 m wide, so panel counts there follow the panel width rather than a post spacing you choose.

The formulas

Every number above comes from four short formulas, and you can check any of them on paper in under a minute. Start by dividing the fence into sections — the bays between posts.

• Sections = total length ÷ post spacing, rounded up. You cannot have part of a section, so 100 ft at 8 ft spacing is 12.5, which rounds up to 13 sections. The last section is simply a little shorter than the rest.
• Posts = sections + 1, plus 1 extra post per gate. Add one more post for each gate opening.
• Rails = sections × 2, or sections × 3. Fences under 6 ft get two horizontal rails per section; fences 6 ft or taller get three, because a taller fence catches more wind and flexes more.
• Pickets = total length in inches ÷ (picket width + gap), rounded up. Then add your waste percentage and round up again, because you cannot buy part of a picket.
• Concrete = posts × 2 bags. Panels, when you choose that style, are simpler still: one panel per section, so panels = sections.

People most often ask why posts are always one more than sections. Picture a short run of fence: it has a post at the start and a post at the end, with sections strung between them, like fence panels on a string. One section needs two posts, two sections share the middle post and need three, and so on. Every run of fence has a post at both ends, so the count is always sections plus one — forgetting that last post is the single most common ordering mistake.

Worked example

Take the 100 ft privacy fence from the quick answer table: 6 ft tall, posts every 8 ft, pickets 5.5 in wide with no gap, no gates, and no waste allowance, so you can follow the raw numbers.

• Step 1 — sections: 100 ft ÷ 8 ft = 12.5, rounded up to 13 sections.
• Step 2 — posts: 13 sections + 1 = 14 posts.
• Step 3 — rails: the fence is 6 ft tall, so 13 sections × 3 rails = 39 rails.
• Step 4 — pickets: 100 ft is 1,200 inches, and 1,200 ÷ 5.5 = 218.18, rounded up to 219 pickets.
• Step 5 — concrete and post length: 14 posts × 2 bags = 28 bags of concrete before waste, and each post needs to be 6 ft + 2 ft buried = 8 ft long.

Those are exactly the numbers the calculator gives for the same inputs, so you can trust it for your own length — and if you add the default 5% waste allowance, the picket count rises to 230, which covers cuts and the odd split board.

6 ft vs 8 ft post spacing

8 ft is the standard spacing, and it is cheaper. It uses fewer posts, fewer holes and less concrete — a 100 ft fence needs 14 posts at 8 ft spacing against 18 at 6 ft — and standard rails and pre-made panels are made to span it. For most garden fences in ordinary conditions, 8 ft is the sensible default.

6 ft spacing is stronger. Choose it in high-wind areas where a fence takes a real battering, for heavy panels that would flex or bow on a longer span, or for tall fences, which act like sails. The extra posts also help on exposed corners and on ground that slopes, where shorter sections are easier to keep level. You pay for the extra posts and concrete, but you get a fence that stays straight.

Pickets vs pre-made panels

Pre-made panels are faster. A panel fills a whole section in one lift, so a straight, level fence goes up quickly with fewer pieces to handle, and the cost per section is easy to price. The trade-off is flexibility: a rigid panel cannot follow sloping ground without being stepped, leaving triangular gaps underneath, and a damaged panel usually means replacing the whole panel.

Individual pickets are slower to fit, one board at a time, but they follow the ground as it rises and falls, so the top and bottom of the fence can track a slope smoothly. They are also easier to repair — one broken picket is a five-minute swap — and you can set the gap yourself, from tight privacy boards to an open picket look, using the same posts and rails.

Gates, corners and concrete

A gate hangs from a post and latches to another, so each gate opening needs its own support. That is why the calculator adds one extra post per gate on top of the normal count: the run is broken at the gate, and a new end post appears. Corners work the same way in practice — a corner post carries fences running in two directions and takes more strain, so many builders use a larger post there. Count your total length along all sides, then add gate posts for each opening.

Gate hardware is not counted in these results. Hinges, a latch, and often a diagonal brace or an anti-sag kit are bought separately, and a wide gate may need a wheel or a double-leaf design. Budget for those on top of the timber and concrete.

The concrete figure is an estimate of 2 × 50 lb bags per post, based on a 4×4 post in a hole about 24 in deep. A wider or deeper hole, a 6×6 post, or loose soil will use more; a narrow hole in firm ground may use less. As a rule for depth, bury at least one-third of the above-ground height, with a 24 in minimum, and go below the frost line where that applies in your area, so frost cannot heave the post out of line.

Before you dig

In the US, call 811 — or use your local service — to have underground utilities marked before digging any post hole. It is free, it usually takes a few days, and it is the step that stops you putting a post hole through a gas, electric, water or data line. Wherever you live, use the equivalent local service before you dig; lines are often much shallower than people expect.

Also check your property line before the first hole, so the fence goes on your land and not your neighbour’s, and check your local permit and HOA rules. Those rules vary by area — height limits, materials and permit requirements differ from place to place — so there is no single universal rule; a short check with your local authority now is far cheaper than moving a fence later.

Fence guides

Prefer to work through the reasoning behind the numbers? These two guides explain the maths this calculator uses, step by step:

• How Many Fence Panels Do I Need?
• Fence Post Calculator — Spacing, Depth & Concrete per Post

Frequently asked questions