Concrete Calculator
Calculate how much concrete you need for a slab, footing or column with this free online concrete calculator, in cubic yards or m³ plus 80, 60 or 40 lb bags.
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Part of the toolkit
How to use Concrete Calculator
- 1Choose a slab/footing, a round column or a hollow tube, and feet/inches or meters/centimeters
- 2Enter the dimensions, how many you're pouring and a waste allowance (5–10% is typical)
- 3Press Calculate concrete to get cubic yards, cubic meters and the number of premix bags
Frequently asked questions
How much concrete do I need for a 10×10 slab?▾
A 10 × 10 ft slab 4 inches thick is 33.3 cubic feet, or 1.23 cubic yards. With 10% extra for waste that's about 1.36 cubic yards — roughly 62 bags of 80 lb premix.
How do I calculate cubic yards of concrete?▾
Multiply length × width × thickness in feet (4 inches = 0.333 ft) to get cubic feet, then divide by 27. For round columns use π × radius² × height.
How many bags of concrete make a yard?▾
About 45 bags of 80 lb (0.6 ft³ each), 60 bags of 60 lb (0.45 ft³) or 90 bags of 40 lb (0.3 ft³) per cubic yard.
How much extra concrete should I order?▾
Add 5–10% for spillage, uneven ground and form flex. Running short mid-pour causes a cold joint, so it's better to have a little left over.
How thick should a concrete slab be?▾
4 inches (10 cm) is standard for patios, walkways and shed floors; driveways usually use 5–6 inches (12–15 cm), especially for heavier vehicles.
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