Concrete Bags Calculator
How many bags of premixed concrete you need for a slab or pad.
Inputs
m
m
mm
%
kg/m³
Typical premix yields 0.017 m³ (0.6 ft³) per 80 lb bag
Results
- Bags needed
- 57 bags
- Concrete volume
- 0.66 m³
- Yield per bag
- 0.0117 m³
Formula
Volume = L × W × Thickness × (1 + waste)
Yield per bag = bag mass ÷ mixed density
Bags = ⌈Volume ÷ Yield⌉
Assumptions & limits
- Check the yield printed on your bag — brands vary.
Worked example
0.66 m³ ÷ 0.01174 m³ per 25 kg bag = 56.2 → 57 bags.