The number of gallons a bag of concrete makes depends on the its density, which can vary slightly depending on factors such as composition and manufacturer. However, as a rough estimate, an 80lb bag of concrete mix can make about 4.5 gallons of concrete, a 60lb bag typically yields about 3.5 gallons, and a 40lb bag can make approximately 2.25 gallons of concrete.

To calculate the volume of a bag of concrete (like 90 lb, 80 lb, 60 lb, 50 lb and 40 lb) in gallons, multiply its yields in cubic feet by 7.481 (since 1 cubic foot = 7.481 US gallons liquid)). To find out volume of concrete bag in cubic feet, you can divide weight of a concrete bag in pounds by 133 (since, 1 cubic foot pre-mix concrete weight = 133 pounds).

Formula to convert cubic feet of concrete to gallons: write down the volume expressed in cubic feet. Multiply this number by 7.481 to convert to US gallons. So, one cubic foot of concrete converted to gallon equals to 7.481 gal.

For example, an 80-pound bag of concrete mix can produce about 0.6 cubic feet of concrete, which is equivalent to about 0.022 cubic yards or 4.5 gallons of concrete. Volume of an 80 pound bag in cubic feet = 80/133 = 0.6 cubic feet, volume in cubic yards = 0.60/27 = 0.022 cubic yards, and volume in gallons = 0.6 × 7.481 = 4.49 or rounded to 4.5 gallons.

A 90-pound bag of concrete mix can make about 0.68 cubic feet of concrete, which is equivalent to about 0.025 cubic yards or 5 gallons of concrete. Volume of a 90 pound bag in cubic feet = 90/133 = 0.68 cubic feet, volume in cubic yards = 0.68/27 = 0.025 cubic yards, and volume in gallons = 0.68 × 7.481 = 5.08 or rounded to 5 gallons.

A 60-pound bag of concrete mix can make about 0.45 cubic feet of concrete, which is equivalent to about 0.017 cubic yards or 3.5 gallons of concrete. Volume of a 60 pound bag in cubic feet = 60/133 = 0.45 cubic feet, volume in cubic yards = 0.45/27 = 0.017 cubic yards, and volume in gallons = 0.45 × 7.481 = 3.36 or rounded to 3.5 gallons.

A 50-pound bag of concrete mix can make about 0.375 cubic feet of concrete, which is equivalent to about 0.014 cubic yards or 3 gallons of concrete. Volume of a 50 pound bag in cubic feet = 50/133 = 0.375 cubic feet, volume in cubic yards = 0.375/27 = 0.014 cubic yards, and volume in gallons = 0.375 × 7.481 = 2.8 or rounded to 3 gallons.

A 40-pound bag of concrete mix can make about 0.30 cubic feet of concrete, which is equivalent to about 0.011 cubic yards or 2.25 gallons of concrete. Volume of a 40 pound bag in cubic feet = 40/133 = 0.30 cubic feet, volume in cubic yards = 0.30/27 = 0.011 cubic yards, and volume in gallons = 0.30 × 7.481 = 2.24 or rounded to 2.25 gallons.

**Here`s are table for how many gallons does a bag of concrete make:**

WEIGHT OF CONCRETE BAG | VOLUME OF CONCRETE BAG IN GALLONS |

90-POUND BAG | 5 Gallons |

80-POUND BAG | 4.5 Gallons |

60-POUND BAG | 3.5 Gallons |

50-POUND BAG | 3 Gallons |

40-POUND BAG | 2.25 Gallons |

**Here’s are general estimate for how many gallons does a bag of concrete make**:

- A 90 lb bag of concrete mix can make approximately 5 gallons of concrete.
- An 80 lb bag of concrete mix can make approximately 4.5 gallons of concrete.
- A 60 lb bag of concrete mix can make approximately 3.5 gallons of concrete.
- A 50 lb bag of concrete mix can make approximately 3 gallons of concrete.
- A 40 lb bag of concrete mix can make approximately 2.25 gallons of concrete.

**Conclusions**:

In general, a 80lb bag of concrete is about 4.5 gallons, a 90lb bag is about 5 gallons, a 60lb bag is about 3.5 gallons, a 50lb bag is about 3 gallons, and a 40lb bag of concrete is about 2.25 gallons.