๐งฑ Concrete Calculator
Enter the length, width, and thickness of the area you're pouring โ a patio, walkway, or slab โ to calculate the required concrete volume in cubic meters and liters. Includes an adjustable waste margin for buffer.
How to use
- Enter the length and width of the area to be poured (in meters).
- Enter the pour thickness (in centimeters).
- Set a waste percentage to see the required volume including a safety margin, calculated automatically.
How the calculation works
This tool works out how much concrete you need for a flat pour such as a slab or floor. Area (mยฒ) = length (m) ร width (m) Volume (mยณ) = area ร thickness (cm) รท 100 Volume with waste = volume ร (1 + waste % รท 100) In litres = volume (mยณ) ร 1,000 Ready-mix concrete is ordered by the cubic metre. Formwork bulging, uneven ground and concrete left in pumps and tools mean more is used than calculated, so a waste allowance adds a margin.
Worked example
Length 4 m, width 3 m, thickness 10 cm, 10% waste Area: 12 mยฒ Volume: 12 ร 0.1 = 1.2 mยณ With waste: 1.2 ร 1.1 = 1.32 mยณ (1,320 litres) For a small job with bagged ready-mix (roughly 12 litres per 25 kg bag), that would be about 110 bags.
Things to be aware of
- Ready-mix suppliers often have a minimum order (commonly 0.25โ1 mยณ). Check with the plant beforehand.
- Driveway slabs that carry cars are usually 10โ15 cm thick with steel mesh to control cracking.
- A cubic metre of concrete weighs about 2.3 tonnes โ worth remembering if you plan to move it by hand.
FAQ
What waste percentage should I use?
To account for ground irregularities and pouring losses, a margin of around 5-10% is commonly used. Adjust based on your site conditions.
How is ready-mix concrete typically ordered?
Ready-mix concrete is usually ordered in supplier-defined units, such as 0.25mยณ or 1mยณ increments. Use this calculator's result as a guide and round up to your supplier's minimum order unit.
Can I use this for bagged concrete mix from a DIY store?
Yes. Divide the volume (in liters) calculated here by the yield per bag listed on your product's packaging to estimate how many bags you'll need.