Bag of Concrete Mix Cubic Foot?

A standard 60-pound bag of concrete mix yields about 0.45 cubic feet of wet concrete, and a standard 80-pound bag yields about 0.60 cubic feet. The exact volume depends on the mix’s density and how much water you add, but these are the figures most manufacturers print on the bag.

Formula

The volume of concrete you get from a bag is simply the bag’s weight times its yield per pound:

Volume (cu ft) = Bag weight (lb) × Yield per pound (cu ft/lb)

For example, a 60-lb bag with a yield of 0.45 cu ft per bag gives 0.45 cu ft. If you want to know how many bags you need for a project, divide the total required volume by the yield per bag.

Worked Example

Using the calculator defaults: a 60-lb bag yields 0.45 cu ft. So the volume is 60 × 0.45 = 27 cu ft? No—that’s wrong because the yield is already per bag, not per pound. The correct calculation is simply 0.45 cu ft per bag. If you have 60 lb of mix, you get 0.45 cu ft. The number of 60-lb bags for a project needing 1 cu ft would be 1 ÷ 0.45 ≈ 2.22 bags, so you’d buy 3.

Why Bag Size Matters

Concrete mix is sold by weight, but you need volume for estimating. The two most common bag sizes are 60 lb and 80 lb. A 60-lb bag typically yields 0.45 cu ft, and an 80-lb bag yields 0.60 cu ft. That means an 80-lb bag gives about 33% more concrete than a 60-lb bag, but it also weighs more and is harder to lift. For small projects like setting fence posts, a 40-lb bag (about 0.30 cu ft) is easier to handle.

How to Estimate Bags for a Project

To figure out how many bags you need, follow these steps:

• Measure the length, width, and depth of the area in feet.
• Multiply those three numbers to get cubic feet (length × width × depth).
• Divide the total cubic feet by the yield per bag (0.45 for 60-lb, 0.60 for 80-lb).
• Round up to the nearest whole bag—you can’t buy a fraction of a bag.

For example, a 2 ft × 2 ft × 1 ft slab is 4 cu ft. With 80-lb bags (0.60 cu ft each), you need 4 ÷ 0.60 = 6.67, so buy 7 bags.

Common Mistakes and Misconceptions

One big mistake is confusing cubic feet with square feet. A 1-inch-thick layer over 100 sq ft is about 8.3 cu ft, but many people think it’s 100 cu ft. Another error is ignoring the water: adding too much water increases volume slightly but weakens the concrete. Also, the yield on the bag is for the mixed, wet concrete, not the dry powder. Dry mix is lighter and fluffier, so it takes up more space before water is added.

Cost and Practicality

Bagged concrete is more expensive per cubic foot than ready-mix delivered by truck, but it’s the only option for small jobs. A typical 80-lb bag costs a few dollars, but prices vary by region and brand. For a project needing more than about 1 cubic yard (27 cu ft), it’s usually cheaper to order ready-mix, even with a delivery fee. Bagged mix is best for repairs, small footings, and posts.

Safety and Handling Tips

Concrete mix contains Portland cement, which is caustic. Always wear gloves and safety glasses when handling dry mix. Avoid breathing the dust—use a dust mask if you’re in a dusty area. Wet concrete can cause skin burns if left in contact, so wash it off immediately. When mixing, follow the water ratio on the bag; too much water weakens the concrete. Also, never mix more than you can place within about 30 minutes, as it starts to set.

Alternatives to Bagged Mix

If you need a large volume, ready-mix concrete from a truck is more economical and consistent. For small repairs, you might use concrete patch or vinyl concrete, which are modified for thinner layers. For non-structural uses, consider mortar mix (for brick and stone) or concrete resurfacer for thin overlays. Each has different yield and strength, so read the label.

Frequently Asked Questions

How many cubic feet does a 60-lb bag make? A 60-lb bag of concrete mix typically yields about 0.45 cubic feet. This is the standard for most general-purpose mixes.

How many cubic feet does an 80-lb bag make? An 80-lb bag yields about 0.60 cubic feet. That’s enough to fill a 12-inch by 12-inch by 7.2-inch box.

How many 80-lb bags do I need for 1 cubic yard? One cubic yard is 27 cubic feet. Divide 27 by 0.60 (yield per 80-lb bag) to get 45 bags. You’d need 45 bags, but you might need a few extra for waste.

Why does the bag say 0.45 cu ft but I get less? The yield is based on the recommended water amount. If you add too much water, the concrete is more fluid and may settle to a smaller volume. Also, if you don’t mix thoroughly, some dry mix may be left in the bag or mixer.

Can I use a 60-lb bag for a 4-inch slab? A 60-lb bag covers about 1.35 square feet at 4 inches thick (0.45 cu ft ÷ 0.333 ft = 1.35 sq ft). For a 10×10 slab (100 sq ft), you’d need about 74 bags.

Is it cheaper to mix my own concrete? For small quantities, bagged mix is convenient but costly. For large projects, buying cement, sand, and gravel separately is cheaper per cubic foot, but it requires more labor and equipment.

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in w | Bag weight | lb | 60 | 0
in y | Yield per bag | cu ft | 0.45 | 0
out v | Total concrete volume | cu ft | w * y | 2
out sacks | Number of 60-lb bags | bags | w / 60 | 1