How Many Bags of Post Concrete Do I Need Per Fence Post?

Working out how much post concrete you need is an important part of planning a fencing project. Order too little and the installation can come to a stop halfway through. Order without calculating the number of posts properly and it is easy to underestimate the amount required for the complete fence.

For most standard fencing installations, Sky Fencing normally allows approximately 2 x 20kg bags of post concrete per standard fence post.

For posts that are likely to require additional support, such as gate posts or fencing installed in a particularly exposed or windy location, we normally recommend allowing around 3 x 20kg bags per post hole.

These quantities provide a practical starting point for planning a fencing order. The actual amount used can still vary depending on the size of the hole, post dimensions, ground conditions and the individual installation.

Quick Answer: How Many Bags of Post Concrete Per Fence Post?

For most fencing projects, use the following Sky Fencing guide:

For a straightforward fencing job, the easiest calculation is therefore:

Number of standard fence posts × 2 = approximate number of 20kg bags required.

You can browse and order our post concrete alongside the other materials required for your fence.

How Much Post Concrete Do I Need for a Full Fence?

Once you know how many fence posts the project requires, calculating the post concrete is relatively straightforward.

For standard posts, multiply the total number of posts by two.

This is an ordering guide rather than a guarantee that every individual post hole will consume exactly two bags. Some holes may use slightly less, while larger or more difficult holes may require additional material.

Why Does Sky Fencing Normally Allow Two Bags Per Post?

A fence post provides the structural support for the fencing installed between it. For a full-height garden fence, particularly one using taller panels, the post has to support a substantial area of fencing exposed to wind and everyday movement.

Trying to plan a job around the absolute minimum possible quantity of post concrete can leave very little allowance for differences between individual post holes.

Sky Fencing therefore normally works on approximately two 20kg bags per standard fence post when planning a normal fencing project.

This provides customers and installers with a much more useful starting quantity when calculating the materials required for an entire fence.

Does Every Fence Post Use Exactly Two Bags?

No. Two bags is the normal planning allowance for a standard post rather than an exact measurement that applies to every post hole.

Actual usage can be affected by:

• The size of the fence post.
• The depth of the hole.
• The width of the hole.
• The condition of the ground.
• Whether the ground has previously been disturbed.
• Old concrete foundations.
• Loose or collapsing soil.
• The type and height of fencing being installed.
• Whether the post is supporting a gate.
• How exposed the fencing is to wind.

This is why post concrete quantities should be treated as a practical allowance rather than an exact quantity for every hole.

How Many Bags of Post Concrete for a Gate Post?

Gate posts need to deal with more than simply supporting a stationary section of fencing.

The gate places additional load on the post, and repeated opening and closing creates movement that a standard intermediate fence post does not normally experience.

For that reason, Sky Fencing normally recommends allowing approximately 3 x 20kg bags of post concrete per gate post hole.

The exact installation will still depend on the gate, post and ground conditions, but three bags provides a better starting allowance for gate posts than treating them exactly the same as a standard intermediate fence post.

How Much Post Concrete for a Fence in a Windy or Exposed Garden?

Wind exposure is an important consideration when installing fencing.

A full-height fence creates a large surface area, and exposed gardens can place significantly greater loads on the fencing system than a sheltered garden surrounded by buildings, trees or other structures.

For fencing in a particularly exposed or windy location, Sky Fencing normally recommends allowing approximately 3 x 20kg bags of post concrete per post hole.

This provides a larger allowance around the post where a stronger footing is appropriate.

Site conditions should always be assessed properly, particularly where the fence is tall or regularly exposed to strong winds.

Standard Post vs Gate Post vs Exposed Fence

How Much Post Concrete Do I Need for 5 Fence Posts?

For five standard posts:

5 posts × 2 bags = approximately 10 x 20kg bags of post concrete.

If one of those posts is a gate post, the calculation could instead be:

• 4 standard posts = 8 bags.
• 1 gate post = 3 bags.
• Total = approximately 11 bags.

How Much Post Concrete Do I Need for 10 Fence Posts?

For ten standard posts:

10 posts × 2 bags = approximately 20 x 20kg bags.

If the entire fence is being installed in a particularly exposed location and three bags are allowed per post:

10 posts × 3 bags = approximately 30 x 20kg bags.

How Much Post Concrete Do I Need for 15 Posts?

For fifteen standard posts:

15 × 2 = approximately 30 bags.

If there are two gate posts within the project, you could calculate:

• 13 standard posts × 2 = 26 bags.
• 2 gate posts × 3 = 6 bags.
• Total = approximately 32 bags.

How Much Post Concrete Do I Need for 20 Posts?

For twenty standard fence posts:

20 × 2 = approximately 40 x 20kg bags.

At this quantity, the post concrete alone represents a significant part of the overall fencing order, which is why it is worth calculating it before placing the order.

How Much Post Concrete Do I Need for 25 Posts?

For twenty-five standard posts:

25 × 2 = approximately 50 bags.

A project of this size may make buying larger quantities of post concrete particularly useful.

Can I Buy Post Concrete by the Pallet?

Yes. Sky Fencing supplies post concrete as individual 20kg bags and also in full pallet quantities.

Buying post concrete by the pallet can be particularly useful for:

• Large domestic fencing projects.
• Fencing contractors.
• Landscapers.
• Builders.
• Trade customers.
• Commercial fencing projects.
• Projects involving a large number of posts.

For example, a project containing 25 standard fence posts already has an initial allowance of approximately 50 bags.

Large fencing runs can therefore consume substantial quantities of post concrete relatively quickly.

You can order post concrete alongside your fence posts, gravel boards and fence panels.

Why Buying Enough Post Concrete at the Start Matters

Post installation is normally one of the first stages of building a fence.

If you run out of post concrete part way through installing the posts, the rest of the fencing job can be delayed even if all of the panels, gravel boards and other components are already on site.

Calculating the complete quantity before starting makes it easier to:

• Order all the required materials together.
• Keep the installation moving.
• Avoid repeated trips for additional bags.
• Account for gate posts separately.
• Allow more material for exposed areas where required.

Do Concrete Fence Posts Still Need Post Concrete?

Yes. A concrete fence post still needs to be secured correctly in the ground.

The fact that the post itself is made from concrete does not mean that the post can simply be placed directly into the soil without an appropriate footing.

Concrete posts are commonly used with full-height fencing and concrete gravel boards, creating a substantial fencing system.

For a standard concrete intermediate post, Sky Fencing normally uses the same starting allowance of approximately two 20kg bags per post hole.

Do Timber Fence Posts Need Post Concrete?

Post concrete is also commonly used when installing timber fence posts.

For most standard timber post installations, the same initial allowance applies:

Approximately two 20kg bags per standard post hole.

The actual quantity can vary depending on the timber post size and the dimensions of the hole.

You can compare available concrete and timber options in our fence posts range.

Does the Size of the Fence Post Change the Amount of Concrete Required?

Yes, potentially.

Different post sizes occupy different amounts of space inside the post hole and may also require different hole dimensions.

This means that two fencing projects with the same number of posts may not necessarily use exactly the same amount of post concrete.

The two-bag recommendation is therefore best used as a practical starting point for normal fencing installations rather than an exact mathematical quantity for every possible post size.

Does Post Height Matter?

Post height can also affect the overall installation.

For example, a typical fencing system finishing at around 6ft may commonly use an 8ft post, while a full 6ft fence panel installed above a gravel board may require a 9ft post.

We cover this subject separately in our guide to what size fence post you need for a 6ft fence.

The important point is to plan the post, panel, gravel board and foundation as one complete fencing system.

Why the Size of the Post Hole Matters

Post concrete fills the space around the fence post inside the prepared hole.

A larger hole naturally requires more material to fill than a smaller one.

If the hole is:

• Wider than expected.
• Deeper than expected.
• Irregular in shape.
• Partially collapsed.

then the amount of concrete used can increase.

Preparing reasonably consistent post holes makes it much easier to estimate the total amount of post concrete required across a complete fencing run.

Why Ground Conditions Can Change the Amount Required

Ground conditions vary considerably between gardens.

A neat post hole dug into firm undisturbed ground may use a different amount of post concrete from a hole excavated through loose or previously disturbed ground.

Conditions that can affect post holes include:

• Loose garden soil.
• Old flower beds.
• Previous fence foundations.
• Rubble.
• Tree roots.
• Recently excavated ground.
• Wet or unstable soil.
• Old concrete.

If the sides of the post hole collapse while digging, the resulting hole becomes larger and may require more material to fill.

Replacing an Existing Fence

Replacement fencing can sometimes require additional post concrete because removing an old post and its existing foundation can leave a large or irregular hole.

When an old fence is removed, you may uncover:

• Existing concrete.
• Broken timber.
• Loose backfilled soil.
• Rubble.
• Tree or hedge roots.

The new post hole may therefore require more preparation than a completely new installation into undisturbed ground.

Post Concrete for a 6ft Fence

A typical full-height panel fencing system may consist of:

• Fence panels.
• Fence posts.
• Gravel boards.
• Post concrete.
• Suitable fixings.

For each standard post within the run, our normal starting allowance would be around two bags.

For example, if the complete fence requires 12 standard posts:

12 × 2 = approximately 24 x 20kg bags of post concrete.

How Many Posts Do I Need?

You need to know the number of posts before you can calculate the amount of post concrete.

For a simple straight run of panel fencing, you normally need posts:

• At the beginning of the run.
• Between each panel.
• At the end of the run.

Additional posts may be required for:

• Corners.
• Returns.
• Gates.
• Changes in direction.
• Changes in fencing height.

This is why calculating post concrete from the number of panels alone can result in an incorrect quantity.

Example: 10 Fence Panels

Imagine a simple straight run consisting of 10 fence panels.

If this requires 11 standard posts, the post concrete calculation would be:

11 posts × 2 bags = approximately 22 bags.

If two additional gate posts are included:

• 11 standard posts = 22 bags.
• 2 gate posts = 6 bags.
• Total allowance = approximately 28 bags.

Example: 15 Fence Panels

A straightforward run of 15 panels may require 16 posts before any gates, corners or other changes are considered.

Using the standard allowance:

16 × 2 = approximately 32 bags.

This demonstrates why the number of posts rather than the number of panels should be used when calculating post concrete.

Don't Forget Gate Posts

Gate posts are easy to overlook when calculating a complete fencing order.

Because Sky Fencing normally allows three bags for a gate post rather than two, they should ideally be counted separately.

For example:

12 standard posts + 2 gate posts

• 12 standard posts × 2 = 24 bags.
• 2 gate posts × 3 = 6 bags.
• Total = approximately 30 bags.

Post Concrete for Closeboard Fencing

Closeboard fencing creates a substantial and private garden boundary.

Sky Fencing's closeboard fence panels are manufactured in-house in Wickford.

Our appropriate closeboard panels use 19 vertical boards, while many competing alternatives use 18.

Our standard closeboard panels use approximately 47 x 32mm rails, while our Heavy Duty panels use larger 75 x 32mm rails.

We also use 50-micron hot-dipped galvanised nails in our closeboard panels to help resist premature rusting.

When installing closeboard panels, the fence posts still need a suitable footing for the complete fencing system.

For standard posts, approximately two bags per hole remains our normal starting allowance, increasing where additional support is appropriate.

Should I Buy Exactly Two Bags for Every Standard Post?

Two bags per standard post is a useful way of calculating the initial quantity, but it is sensible to remember that individual holes can vary.

If you are installing a large fencing run, particularly into inconsistent or previously disturbed ground, having some additional material available can prevent the job stopping if a handful of holes require more than expected.

Can I Use Less Than Two Bags?

Some smaller or tightly prepared holes may physically consume less material.

However, for the standard full-height fencing projects Sky Fencing commonly supplies, we prefer to calculate using approximately two 20kg bags per standard post.

This gives a more practical ordering quantity than assuming every hole will use the smallest possible amount.

When Should I Allow Three Bags Instead?

Our normal three-bag allowance is particularly relevant for:

• Gate posts where the post supports the weight and movement of the gate.
• Exposed or windy locations where the fencing is likely to experience greater wind loading.

Other unusual site conditions can also mean more material is required.

Should I Order All the Post Concrete at the Same Time?

For most fencing projects, ordering the post concrete alongside the other materials makes planning considerably easier.

Once you know the total number of standard posts, gate posts and any areas requiring additional support, you can calculate the initial quantity before the installation begins.

For larger projects, Sky Fencing also supplies post concrete in pallet quantities, making it easier for trade customers and larger installations to order substantial quantities together.

How to Calculate Your Complete Fencing Order

A simple planning process is:

1. Measure the fencing boundary.
2. Choose the required fence panel type and height.
3. Choose concrete or timber posts.
4. Decide whether gravel boards will be used.
5. Calculate the number of fence panels.
6. Calculate the total number of posts.
7. Separate standard posts from gate posts.
8. Allow two bags for each standard post.
9. Allow three bags for gate posts.
10. Consider three bags per post where the fence is particularly exposed or windy.
11. Add a sensible allowance where ground conditions are likely to result in larger holes.

Common Post Concrete Calculation Mistakes

Calculating One Bag Per Post

For the standard full-size fencing installations Sky Fencing commonly supplies, our normal allowance is approximately two 20kg bags per standard post.

Planning on a single bag for every post can leave little flexibility if holes are larger than expected.

Calculating from the Number of Panels

Post concrete should be calculated from the number of posts, not simply the number of panels.

Forgetting the Final Post

A simple panel run normally needs a post at both ends, meaning the number of posts may be greater than the number of panels.

Forgetting Gate Posts

Gate posts should be included separately because Sky Fencing normally allows three bags per gate post hole.

Ignoring Wind Exposure

An exposed garden can place significantly greater loads on the fence than a sheltered location. We normally allow around three bags per post hole where additional support is required for a particularly exposed or windy fence.

Assuming Every Hole Will Be Identical

Ground conditions can change along the same fence line. One post hole may remain neat while another becomes much larger due to loose ground or an old foundation.

How Many Bags of Post Concrete Do I Need? Final Answer

For most standard fencing installations, Sky Fencing normally recommends approximately 2 x 20kg bags of post concrete per standard fence post.

For posts requiring additional support:

• Standard fence post: approximately 2 bags.
• Gate post: approximately 3 bags.
• Exposed or windy location: approximately 3 bags per post hole.

The amount actually used can vary depending on the size of the post hole, ground conditions, post dimensions and the specific installation.

For larger projects, Sky Fencing supplies post concrete as individual 20kg bags and in full pallet quantities.

You can also order your fence posts, gravel boards, fence panels and closeboard fence panels alongside the rest of the materials required for your project.

Frequently Asked Questions

How many 20kg bags of post concrete do I need per fence post?

For most standard fence posts, Sky Fencing normally allows approximately 2 x 20kg bags per post hole.

How many bags should I use for a gate post?

Sky Fencing normally allows approximately 3 x 20kg bags per gate post hole because gate posts support the additional weight and movement of the gate.

How many bags should I use in a windy garden?

For fencing in a particularly exposed or windy location, we normally recommend allowing approximately 3 x 20kg bags per post hole.

How many bags do I need for 5 fence posts?

Five standard fence posts would require an initial allowance of approximately 10 x 20kg bags.

How many bags do I need for 10 fence posts?

Ten standard fence posts would require approximately 20 x 20kg bags.

How many bags do I need for 15 fence posts?

Fifteen standard posts would require approximately 30 x 20kg bags.

How many bags do I need for 20 fence posts?

Twenty standard posts would require approximately 40 x 20kg bags.

How much post concrete do I need for 25 posts?

Twenty-five standard fence posts would require an initial allowance of approximately 50 x 20kg bags.

Can I buy post concrete by the pallet?

Yes. Sky Fencing supplies post concrete as individual bags as well as full pallet quantities, which can be particularly useful for larger domestic, trade and commercial fencing projects.

Is one 20kg bag enough for a fence post?

For the standard full-size fencing installations Sky Fencing commonly supplies, we normally budget for around two 20kg bags per standard post rather than relying on one bag.

Does every post use exactly two bags?

No. Two bags is a practical starting allowance. The actual quantity can vary depending on hole dimensions, ground conditions and post size.

Do concrete posts need post concrete?

Yes. Concrete fence posts still need to be securely installed into the ground. For a standard concrete post, approximately two bags per hole is our usual starting allowance.

Do timber posts need post concrete?

Post concrete is commonly used to secure timber fence posts as well. Around two 20kg bags per standard post is our normal initial allowance.

Why might one fence post need more concrete than another?

Post holes can vary because of loose soil, old foundations, rubble, roots, collapsing sides or different post sizes. Larger holes naturally require more material.

Should I order extra post concrete?

For larger projects or sites with inconsistent ground conditions, having some additional material available can be useful. This helps avoid stopping the installation if several holes require more than expected.