How Many Bags of Postcrete Per Post?

For most standard domestic fence posts, allow one to two bags of Postcrete per post. A small timber post in firm ground may need one bag, while a larger post or deeper, wider hole will usually need two or more. The right quantity depends mainly on the post dimensions, hole diameter, planting depth and ground conditions.

Always check the coverage and instructions printed on your chosen product because bag weights and stated yields can vary between manufacturers. It is sensible to buy a small amount extra rather than stop work because one hole is larger than expected.

Quick guide: how many bags of Postcrete per post?

The following figures are practical estimates for common garden fencing jobs. They assume typical bagged rapid-setting post concrete and reasonably neat holes. Treat them as a buying guide rather than an exact specification.

• 75mm x 75mm timber post: usually 1 bag in a hole about 200mm wide and 450mm to 600mm deep.
• 100mm x 100mm timber post: usually 1 to 2 bags in a hole about 250mm to 300mm wide and 600mm deep.
• 125mm x 125mm timber gate post: usually 2 to 3 bags, depending on hole width and depth.
• Slotted concrete fence post: commonly 2 bags, but large corner or end-post holes may require 3 bags.
• Heavy gate post: often 3 bags or more because the post needs a wider and deeper foundation.

These quantities assume that some compacted stone or hardcore may be placed beneath the post where appropriate. Do not reduce the foundation merely to save a bag. A sound fence depends on posts that are firmly supported.

What changes the amount you need?

Post size

A larger post displaces more material, but it also normally requires a larger hole. In practice, moving from a small timber post to a heavy concrete or gate post usually increases the overall quantity of Postcrete required.

Hole diameter

Hole width has a major effect on volume. A hole that looks only slightly wider can take considerably more material all the way around the post. Keep holes neat and consistent, but make sure there is enough space for concrete to surround and support the post properly.

Hole depth

A common rule is to place roughly one-third of the post below ground, although the correct depth depends on fence height, exposure and ground conditions. A typical 1.8m fence often uses a post with around 600mm in the ground. Taller fences and exposed positions may need deeper foundations.

Ground conditions

Firm clay can produce a tidy hole, while loose, sandy, wet or made-up ground may collapse and leave a much wider opening. Tree roots, old foundations and removed posts can also create irregular spaces that use more mix than expected.

Post position

End, corner and gate posts take greater loads than intermediate posts. They may need deeper or broader foundations, especially where a gate places a repeated sideways force on its supporting post.

How to estimate the quantity more accurately

You can estimate the concrete volume by calculating the volume of the hole and subtracting the part occupied by the post. For square or rectangular holes, multiply width by length by concrete depth. Then calculate the buried volume of the post and subtract it.

Keep every measurement in metres. For example, 300mm becomes 0.30m and 600mm becomes 0.60m. The result is in cubic metres.

• Hole volume: width x length x concrete depth.
• Buried post volume: post width x post thickness x buried length.
• Concrete required: hole volume minus buried post volume.

Round holes require a circle-volume calculation, but for an everyday material estimate you can use the manufacturer's coverage guide or treat the hole as a slightly larger square. That gives you a useful allowance for uneven sides and minor spillage.

Once you know the approximate concrete volume, compare it with the stated yield per bag. Product yields differ, so the information on the bag should take priority over a general online figure.

Worked example for a six-panel fence

Suppose you are building a straight run using six standard fence panels. This normally requires seven posts: one at each end and five between the panels. You plan to use 100mm x 100mm timber posts, with each post planted 600mm into the ground.

If each hole is around 250mm to 300mm wide, you should plan for approximately two bags per post. The basic calculation is:

• 7 posts x 2 bags = 14 bags.
• Add 1 or 2 spare bags for uneven holes, loose soil or accidental loss.
• A practical order would therefore be about 15 or 16 bags, subject to the chosen product's stated yield.

If you dig clean, narrow holes in firm ground, you may use less. If one end post sits in disturbed soil or a former post hole, it may use more. Unopened surplus may also be useful for another post, provided it is stored dry and within the manufacturer's storage guidance.

Before ordering materials, use our fence calculator to estimate the number of panels, posts and gravel boards required for your run.

Timber posts and concrete posts

The same volume principle applies to both types, but concrete posts are heavier and are commonly used with a substantial foundation. A typical intermediate slotted post may take around two bags. Corner posts, end posts and posts in exposed ground can need more.

Browse our concrete posts if you want a durable system to use with timber or concrete gravel boards. K C Fencing and Timber Ltd can help you choose compatible posts, panels and base components, but we supply materials only and do not provide fitting or installation.

When setting timber posts, avoid leaving a hollow around the post or finishing the concrete so that water collects against the timber. Follow the product instructions, check every post for level and alignment, and support it until the material has set sufficiently.

Common mistakes when buying Postcrete

• Assuming every hole will be identical: loose soil and old foundations often make some holes larger.
• Forgetting end and corner posts: these may need a stronger foundation than intermediate posts.
• Using the post height as the concrete depth: the base may include drainage stone, so measure the actual space to be filled.
• Relying on a universal bag yield: always read the information for the brand and bag size you are buying.
• Ordering the exact minimum: one collapsed hole can leave you short halfway through the job.
• Adding dry mix or water by guesswork: follow the manufacturer's sequence and quantity instructions.

Plan the complete fence before you start digging. Check underground services, boundary lines and local requirements, particularly for taller fences or work beside a road. If you are unsure about foundation sizes for an exposed site, seek appropriate professional advice.

Order fencing materials from K C Fencing and Timber Ltd

K C Fencing and Timber Ltd manufactures and supplies fence panels, posts, gravel boards and other fencing materials for trade and DIY customers. We offer delivery across the West Midlands, including Wolverhampton, Birmingham, Walsall, Dudley, West Bromwich, Wednesbury, Worcester, Redditch, Stourbridge, Kidderminster and Halesowen. Free collection is available from our yard at 83 Portway Road, Wednesbury WS10 7DZ.

For help working out how many bags of Postcrete per post to order, call 01902 288162 or request a quote.