Concrete Calculator
Estimate concrete volume and bags needed for slabs and footings.
Concrete needed
1.36 cu yd
includes 10% overage
Exact volume
1.23 cu yd
80 lb bags
56
60 lb bags
75
Volume with a safety margin
Volume = length × width × depth, with depth converted to feet and the result divided by 27 for cubic yards. Pros order 10% extra — subgrade dips and spillage always eat some — because a short pour mid-slab is far costlier than a little surplus.
Bags vs. ready-mix
An 80 lb bag yields about 0.6 cubic feet, so a 10×10 ft slab at 4 inches needs ~56 bags — around a truck-order threshold. Above roughly one cubic yard, ready-mix delivery usually wins on both labor and consistency; bags win for post holes and small pads.
Frequently asked questions
- How does the Concrete Calculator work?
- Estimate concrete volume and bags needed for slabs and footings.
- Is the Concrete Calculator free to use?
- Yes. The Concrete Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.
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