Postcrete Calculator
Rapid material takeoff for secure fence footings.
Recommendation: 3x the width of the post
Concrete Requirements
The Science of Solid Fence Posts
Rapid-Set Security
A fence is only as strong as its footings. In the UK, the move towards 'Postcrete' has revolutionised fencing, allowing a single person to install a full run of fencing in a single day.
Our **fence post concrete calculator** uses precise volume displacement logic to ensure you don't over-order heavy bags or run short halfway through a job.
Hole Dimension Rules
Avoiding the 'Concrete Collar'
A common mistake is creating a 'collar' of concrete only at the top of the hole. This provides very little structural strength and allows the post to pivot at the base.
Always fill the hole from the bottom up. Ensure the concrete surrounds the entire buried section of the post. For timber posts, it is also wise to leave a small amount of soil/gravel at the very bottom of the hole to allow water to drain out of the end-grain of the timber.
The Water Ratio
Standard Postcrete requires approximately 2 to 3 litres of water per 20kg bag. If the ground is already saturated, you can use slightly less. Over-watering will weaken the final set and increase the curing time.
Bracing is Essential
Because Postcrete sets so quickly, you must have your spirit level ready. Use timber 'props' or braces to hold the post in position before you add water. Once the bubbling stops, the post is locked in.
Pro Tip: Tapered Tops
When the concrete is nearly set, use a trowel to 'slope' the top of the concrete away from the post. This prevents water from pooling around the timber, which is the #1 cause of post rot at ground level.
Postcrete & Footing FAQ
Structural Disclaimer
Concrete requirements are estimates based on standard hole shapes. Irregular holes or 'bell-bottomed' holes dug in sandy soil will require significantly more material. Always keep 2-3 spare bags on site to avoid unfinished posts.