About this calculator
Bagged concrete is sold by weight, but what matters is yield: an 80 lb bag makes about 0.60 cubic feet, a 60 lb bag 0.45, and a 40 lb bag 0.30. Enter your pour's dimensions (or the volume, if you already know it), pick a bag size, and you'll get the count to buy, with a waste allowance so the last corner doesn't come up short.
How the math works
The calculator finds your volume in cubic feet (length × width × thickness, or your entered cubic yards × 27), adds the waste allowance, and divides by the selected bag's yield, rounding up to whole bags. Yields are the manufacturers' published figures for standard concrete mix.
Common questions
How many bags of concrete are in a cubic yard?
About 45 eighty-pound bags, 60 sixty-pound bags, or 90 forty-pound bags make one cubic yard. That number is also the practical ceiling for hand-mixing. At a yard or more, priced ready-mix delivery usually beats bags on both money and effort.
Which bag size should I buy?
The biggest you can comfortably lift and mix. 80 lb bags need the fewest trips and cost the least per cubic foot; 60 lb is the common compromise; 40 lb makes sense for small patches and post-setting.
How much water per bag?
Roughly 3 quarts for an 80 lb bag, 2½ for a 60, and 2 for a 40. But follow the bag and err dry: you can always add water, and soupy mix is weak mix.