Frequently Asked Questions
How much concrete do I need for a slab?
Multiply the length, width, and depth of the pour (in consistent units) to get the volume. For a slab 3m long, 2m wide, and 10cm deep, that's 3 × 2 × 0.1 = 0.6 cubic meters. This calculator does that conversion for you and adds a waste buffer on top.
Why is there a waste buffer built in?
Real pours rarely use exactly the calculated volume — uneven ground, formwork gaps, and spillage all eat into your premix. A 5–10% buffer is standard practice so you don't end up short mid-pour, which is far more disruptive than having a little extra.
How accurate is the bag count?
It uses typical published yield figures per bag size (how much concrete volume one bag makes once mixed with water), which is standard across most major premix brands but can vary slightly — check your specific bag's packaging for its exact yield if precision matters.
What depth should I use for a typical slab?
A general-purpose patio or shed base is commonly poured around 10cm (4in) deep; a driveway or anything load-bearing for vehicles is usually thicker (15cm/6in or more). Check local building requirements for anything structural.