Is 10 inches wide enough in soft ground?

It may not be. Loose sand, soft clay and made ground all hold a post less well, and the usual response is a wider hole rather than a deeper one, because the resistance to a fence being pushed over comes largely from the width of the footing. A local contractor will know what the soil there needs.

How much difference does going to 12 inches make?

Considerably more than it sounds. Volume grows with the square of the radius, so widening from 10 to 12 inches raises the concrete needed by roughly 45% while the hole only looks two inches bigger. It is the single most sensitive input in the whole calculation.

Can I mix in the hole rather than in a barrow?

Some fast-setting products are designed for it: dry mix into the hole, then water on top. Ordinary bagged concrete is not, and mixing it dry in the hole tends to leave pockets that never hydrate. Follow the specific product instructions rather than a general rule.

Fence Ledger

How much concrete for a 4x4 post in a 10 inch hole?

Ten inches is the usual hole for a 4x4 post, being roughly three times the width of the post, and it is the size most residential fences are actually built at.

Concrete per post

1.71 bags

Based on a 10 in hole, 30 in deep, on a 4 in gravel base.

What the usual answer misses

Two deductions separate the honest number from the arithmetic most calculators do. The gravel base at the bottom of the hole is not concrete, and on a typical hole it accounts for a noticeable share of the depth. The post itself displaces concrete too, and the displacement has to be computed from its real 3.5 inch section rather than the four inches on the label — using the nominal size overstates what the post takes up by about a third.

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

222

Concrete

24 bags

Estimated cost

Materials only (DIY)

$1,000 – $2,600

Professionally installed

$2,700 – $6,100

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, angi.com, ergeon.com, homewyse.com

Shopping list

Bill of materials for this fence
Material	Size	Quantity
Posts	4x4	14
Rails incl. waste	2x4	40
Pickets incl. waste	1x6	222
Concrete mix		24bags
Gravel		6bags
Exterior screws		≈1,500
Walk gate kit		1

Why these numbers

How we got the section count

Run 1: 96 ft ÷ 8 ft = 12, rounded up to 12 sections

How we got the post count

3 posts are fixed by the shape itself
2 at the open ends
1 carrying a gate
11 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
96 ft of fence needs 201 pickets
Plus 10% for offcuts, rounded up to 222

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

Is 10 inches wide enough in soft ground?: It may not be. Loose sand, soft clay and made ground all hold a post less well, and the usual response is a wider hole rather than a deeper one, because the resistance to a fence being pushed over comes largely from the width of the footing. A local contractor will know what the soil there needs.
How much difference does going to 12 inches make?: Considerably more than it sounds. Volume grows with the square of the radius, so widening from 10 to 12 inches raises the concrete needed by roughly 45% while the hole only looks two inches bigger. It is the single most sensitive input in the whole calculation.
Can I mix in the hole rather than in a barrow?: Some fast-setting products are designed for it: dry mix into the hole, then water on top. Ordinary bagged concrete is not, and mixing it dry in the hole tends to leave pockets that never hydrate. Follow the specific product instructions rather than a general rule.