Hole Sizes for Fence Posts and Posts

Summary: If you need to install a fence post or other post type find out how deep the hole should be in order for it to remian in place and upright

Don't want to do this job yourself? Let us help you find a tradesman local to you

A common question that we get asked is "How do I work out the size of hole I need for a fence post?"

The posts can either be fence posts or washing line posts. The general rule of thumb is that when setting a post into the ground, the height required above the ground should be divided by 3 and this figure is the depth of the hole.

Fence post correctly set in ground

Fence post correctly set in ground using Postcrete

For example, if you are erecting a 6 foot high fence the posts need to be 6 feet above the ground. 6 divided by 3 is 2, therefore the depth of the hole required is 2 feet.

The width of the post hole should be 3 times the width of diameter of the post.

Please use our table below to work out the width and depth of hole required for your posts. Please note the below requirements are specific for premixed concrete such as Postcrete mentioned here.

Post size Height of post above ground Hole size (width x depth) No of 20kg bags of premixed Concrete required
50mm (2”) 90cm (3') 15cm (6”) x 30cm (12”) 1/3 of a bag
  1.2m (4') 15cm (6”) x 40cm (18”) 1/2 bag
  1.8m (6') 15cm (6”) x 60cm (24”) 3/4 of a bag
75mm (3”) 90cm (3') 23cm (9”) x 30cm (12”) 1 bag
  1.2m (4') 23cm (9”) x 40cm (18”) 1 and 1/3 bags
  1.8m (6') 23cm (9”) x 60cm (24”) 1 and 1/2 bags
100mm (4”) 90cm (3') 30cm (12”) x 30cm (12”) 1 and 3/4 bags
  1.2m (4') 30cm (12”) x 45cm (18”) 2 bags
  1.8m (6') 30cm (12”) x 60cm (24”) 2 and 3/4 bags

If you would like to find out how to mix the concrete for your fence post click through to our mixing concrete project.

Alternatively if you only require a small amount to concrete a small fence post or repair an area of concrete then your local DIY shed should have a range of DIY pre mixed and ready mix concretes ideal for fixing fence posts.

Don't fancy doing this project yourself? We work with Plentific to ensure that we recommend only reliable and trustworthy tradesmen.

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