How Many Bags of Concrete Do I Need?
Bags are convenient for small pours and expensive for big ones. The math is simple once you know each bag’s yield.
The bag math
Work out your volume in cubic feet (length × width × thickness in feet), then divide by the bag yield: 0.45 for a 60 lb bag, 0.6 for an 80 lb. A 3 ft × 3 ft × 4 in pad is 3 cubic feet — about seven 60 lb bags. The concrete calculator does this for any shape.
When to stop buying bags
Bags make sense up to roughly a cubic yard (about 45–60 bags). Beyond that, the cost, mixing time and consistency all favor a ready-mix truck. Keep both your bag price and local ready-mix price in your pricebook so the break-even is obvious.
FAQ
How many 60 lb bags of concrete in a cubic yard?
About 60 bags (a 60 lb bag yields ~0.45 cu ft, and a cubic yard is 27 cu ft).
How many 80 lb bags in a cubic yard?
About 45 bags (an 80 lb bag yields ~0.6 cu ft).
When should I use ready-mix instead of bags?
Once you pass roughly one cubic yard (45–60 bags), ready-mix is usually cheaper, faster and more consistent.