Concrete Calculator
Calculate concrete needed in cubic yards, meters, and bags for your project.
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Quick Tip
Choose feet or metres, then enter length and width.
About This Tool
Why use Concrete Calculator?
Enter the length, width and depth of a slab, footing or pad and this calculator returns the concrete needed in cubic yards, cubic metres and cubic feet, plus how many 80 lb and 60 lb bags that represents and the approximate weight.
Depth is entered in inches when you work in feet, or centimetres when you work in metres, because that is how slabs are specified. An 80 lb bag yields about 0.6 cubic feet and a 60 lb bag about 0.45, so a 10 ft × 10 ft slab at 4 inches deep (33.3 cu ft) needs roughly 56 bags of 80 lb — the point at which ready-mix delivery is usually cheaper and easier. Order 5–10% extra for uneven subgrade and spillage.
Key Benefits
Bags and ready-mix in one view
80 lb and 60 lb bag counts alongside cubic yards, which is the decision point between mixing and ordering.
Weight estimate included
Concrete weighs roughly 2,400 kg per cubic metre (about 150 lb per cubic foot), which matters for transport and formwork.
Depth in practical units
Inches with feet, centimetres with metres, the way slab thickness is actually specified.
How to use Concrete Calculator
- 1
Choose feet or metres, then enter length and width.
- 2
Enter the depth in inches (feet mode) or centimetres (metre mode). Four inches is typical for a domestic slab.
- 3
Read the volume in cubic yards for ready-mix orders, or the bag counts for small pours.
- 4
Add 5–10% to the order for waste and uneven ground.
Best use cases
Order ready-mix for a driveway, shed base or patio.
Count bags for fence posts or a small pad.
Compare the cost of bagged concrete against delivery.
Check a contractor's quantity before accepting a quote.
Concrete Calculator FAQs
How many 80 lb bags of concrete are in a cubic yard?
About 45, since each bag yields roughly 0.6 cubic feet and a cubic yard is 27 cubic feet. With 60 lb bags it is about 60.
How thick should a concrete slab be?
Four inches (100 mm) is standard for patios, paths and shed bases. Driveways carrying vehicles are usually 5–6 inches, often with reinforcement.
How much extra concrete should I order?
5–10% over the calculated volume. Subgrade is rarely perfectly level, and running short mid-pour creates a cold joint.
How much does concrete weigh?
About 2,400 kg per cubic metre, or roughly 150 lb per cubic foot. A cubic yard weighs around 1.8 tonnes.
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