Why does adding a gate add a post?

A gate needs a post on each side to hang from and latch to. The opening removes fence, but the two posts framing it are still posts — so a gate in the middle of a run adds one net post compared with the same run without it.

Can I space posts further apart to use fewer?

Up to a point. Rail stock is commonly 8 ft, so spacing beyond that means cutting and joining rails mid-span, which is weaker and wastes material. Wider spacing also sags more, especially on tall privacy fence.

Does the corner post need to be bigger?

Corner and gate posts carry more load than line posts, and many builders use a 6×6 or set them deeper. The calculator counts them separately so you can order the right mix.

Fence Ledger

How many fence posts do I need for 100 feet?

One hundred feet of fence at standard 8 ft spacing needs a specific number of posts, and it is not simply 100 divided by 8.

Posts needed

13 sections at 8 ft spacing.

What the usual answer misses

A run of fence needs one more post than it has sections — the fence posts are the fence posts plus the one at the far end. What changes that count is anything that forces a post: a corner, a gate, or the end of an open run. Add a single gate to this same 100 ft and the count goes up, not down, even though there is less fence.

Work out your own

Every assumption above is editable. Change the length, the spacing, the hole size — the numbers and the working update as you go.

Units

Shape

Fence length

Height

Gates

Advanced options

These are typical values, not requirements. Post depth in particular is governed by your local frost line and building code — check before you dig.

Post spacing

Gate width

Picket gap

Hole diameter

Hole depth

Gravel base

Bag yield

Waste allowance

Posts

Sections

Pickets

230

Concrete

24 bags

Estimated cost

Materials only (DIY)

$800 – $2,000

Professionally installed

$2,500 – $5,500

National planning ranges compiled from published US construction cost guides, last checked September 2026 (confidence: medium-low). Prices vary sharply by region, season and contractor. These are estimates for planning, not quotes.

Sources: homeguide.com, calcsummit.com, ergeon.com, homewyse.com

Shopping list

Bill of materials for this fence
Material	Size	Quantity
Posts	4x4	14
Rails incl. waste	2x4	43
Pickets incl. waste	1x6	230
Concrete mix		24bags
Gravel		6bags
Exterior screws		≈1,500

Why these numbers

How we got the section count

Run 1: 100 ft ÷ 8 ft = 12.5, rounded up to 13 sections

How we got the post count

2 posts are fixed by the shape itself
2 at the open ends
12 line posts spaced between them
14 posts in total

How we got the picket count

Each picket covers 5.5 in plus a 0.25 in gap, so they repeat every 5.75 in
100 ft of fence needs 209 pickets
Plus 10% for offcuts, rounded up to 230

How we got the concrete

Each 10 in hole is 30 in deep, less 4 in of gravel base, leaving 26 in of concrete
The 4x4 post itself takes up part of that, so each hole needs the remainder
Across 14 posts
Divided by the 0.6 cu ft a bag yields: 23.27, so buy 24 bags

Common questions

Why does adding a gate add a post?: A gate needs a post on each side to hang from and latch to. The opening removes fence, but the two posts framing it are still posts — so a gate in the middle of a run adds one net post compared with the same run without it.
Can I space posts further apart to use fewer?: Up to a point. Rail stock is commonly 8 ft, so spacing beyond that means cutting and joining rails mid-span, which is weaker and wastes material. Wider spacing also sags more, especially on tall privacy fence.
Does the corner post need to be bigger?: Corner and gate posts carry more load than line posts, and many builders use a 6×6 or set them deeper. The calculator counts them separately so you can order the right mix.