Calculators/ Concrete/Concrete Bag Calculator
Concrete Bag Calculator
How many 40, 60 or 80 lb bags of concrete do you need?
Concrete Bag Calculator
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Bagged concrete is sold by weight but used by volume, which is why the bag count is never obvious. This converts your dimensions into a bag count for all three common bag sizes.
How this is calculated
- Volume in cubic feet = length × width × thickness ÷ 12.
- Each 80 lb bag yields about 0.60 ft³ of mixed concrete, a 60 lb bag 0.45 ft³, and a 40 lb bag 0.30 ft³.
- Divide total volume by the bag yield and round up: you cannot buy part of a bag.
Frequently asked questions
How many 80 lb bags make a cubic yard?
Forty-five. A cubic yard is 27 cubic feet and each 80 lb bag yields 0.60 cubic feet.
Is bagged concrete cheaper than ready-mix?
Only for small pours. Below about half a cubic yard bags win. Above that, ready-mix is cheaper per yard and saves hours of mixing.
How much water does a bag of concrete need?
Roughly 3 quarts for an 80 lb bag, but always follow the printed instructions. Too much water is the most common cause of weak, cracking concrete.