Concrete Calculator
Enter slab dimensions, get volume in m³, yd³, ft³, and number of 80-lb bags.
For Slabs, Footings, and Columns
This calculator handles rectangular volumes: length × width × thickness. The result converts to all the units you'd actually order concrete in — cubic meters, cubic yards, cubic feet, and pre-mix bags.
Frequently Asked Questions
How much concrete per 80-lb bag?
One 80-lb (36 kg) bag of pre-mix yields about 0.023 m³ (0.6 ft³) of concrete — roughly a 60×60×10 cm slab section.
Volume formula for a slab?
Volume = Length × Width × Thickness. A 3×3 m slab, 10 cm thick = 0.9 m³ of concrete — about 40 bags of 80-lb pre-mix.
How many bags vs ready-mix truck?
Above 1 m³ (1.3 yd³), ordering a ready-mix truck is usually cheaper and faster than mixing bags. Trucks deliver ~5–9 m³ at a time.
Should I order extra?
Add 5–10% to your calculated volume. You can always dump extra into forms or use it for a small pad — running short is a disaster mid-pour.