How Much Postcrete Do You Need Per Fence Post?
Not sure how many bags of Postcrete to use per fence post? This quick guide explains how much you’ll need for different post sizes, depths, and fence types, plus tips for mixing and setting posts correctly.
Rapid Set Post Concrete 20kg Bag
Why Getting the Right of Postcrete Amount Matters
Using the right amount of Postcrete is key to keeping your fence secure and upright for years to come.
Too little, and posts can lean or loosen over time. Too much, and you’re simply wasting materials and money.
As a general rule, each post hole should be filled to around one-third of its depth with concrete, ensuring the post is firmly anchored below the frost line and supported evenly all around.
At Clarke Fencing, we recommend Postcrete 20kg bags for all standard domestic and trade fence installations.
Recommended Amount of Postcrete Per Fence Post
The number of bags you need depends on hole size, post thickness, and fence height.
| Post Size | Hole Depth | Typical Fence Height | Recommended Bags of Postcrete (20kg) |
|---|---|---|---|
| 75mm x 75mm (3″) | 600mm (2ft) | Up to 1.2m (4ft) | 1.5 bags |
| 100mm x 100mm (4″) | 600mm (2ft) | Up to 1.8m (6ft) | 1.5–2 bags |
| 125mm x 125mm (5″) | 750mm (2.5ft) | 1.8m–2.4m (6–8ft) | 2–3 bags |
| 150mm x 150mm (6″) | 900mm (3ft) | 2.4m+ (8ft+) | 3+ bags |
Pro tip:
It’s always best to round up — having an extra bag or two on site is much cheaper than leaving posts half-set.
How to Calculate Postcrete Requirements for a Full Fence Line
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Count your total posts — for example, 8 posts in a 7-panel run.
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Multiply by the recommended amount from the table above.
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e.g. 8 posts × 2 bags = 16 bags total.
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Add 1–2 spare bags for safety or corner posts, which often need more due to wider holes or angled alignment.
If you’re installing closeboard fencing, heavy-duty panels, or gate posts, always use at least 2 full bags per post for maximum strength.
How to Mix and Pour Postcrete
Postcrete is ready-to-use — no separate cement or aggregate needed.
Follow these steps for the best results:
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Position your post in the hole and use a level to check it’s upright.
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Pour the dry Postcrete evenly around the post until the hole is roughly two-thirds full.
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Add water — about 2–2.5 litres per 20kg bag (or follow bag instructions).
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Mix quickly with a stick or trowel to ensure even wetting.
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Hold the post steady for 3–5 minutes while it sets.
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Allow 10–15 minutes before moving on to the next post, and 24 hours before applying strain or attaching fence panels.
Setting Depth and Stability Tips
For a strong, long-lasting fence:
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Dig at least 600mm (2ft) deep
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Widen the base of the hole slightly for better grip.
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Slope the top of the Postcrete away from the post to shed rainwater.
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Use a Post Saver Sleeve for extra rot protection at ground level.
Should You Mix Your Own Concrete Instead?
For most homeowners and small jobs, Postcrete is faster and cleaner — it’s premixed and sets in under 10 minutes.
If you’re setting dozens of posts, you can save money by mixing your own concrete (5:1 ballast to cement ratio), but you’ll trade off convenience and speed.
For DIY projects, Postcrete remains the most efficient and reliable choice.
For More info on Cement Read our Guide How to Make Cement for Fence Posts, Bases & Garden Projects
Clarke Fencing Ltd — Supplying quality fencing and landscaping materials across Suffolk and East Anglia since 1984.
