How Many Cubic Feet in a Bag of Concrete? (40, 50, 60, 80 lb)

How many cubic feet in a bag of concrete: an 80 lb bag yields about 0.60 cubic feet of mixed concrete, a 60 lb bag yields 0.45, a 50 lb bag yields 0.375, and a 40 lb bag yields 0.30. Put another way, that is 45, 60, 72, and 90 bags per cubic yard. Those are the standard published yields for common bagged concrete mix.

Concrete bag yield chart

Here is every common bag size, the volume of mixed concrete it makes, and how many bags it takes to fill one cubic yard. Pin this. It answers most of the question on its own.

• 80 lb bag, 0.60 cubic feet, 45 bags per cubic yard
• 60 lb bag, 0.45 cubic feet, 60 bags per cubic yard
• 50 lb bag, 0.375 cubic feet, 72 bags per cubic yard
• 40 lb bag, 0.30 cubic feet, 90 bags per cubic yard

One cubic yard is 27 cubic feet. That is the only conversion you need to move between the two units. If you would rather skip the arithmetic, punch your dimensions into the Concrete Calculator and it returns the bag count for each size.

What does bag yield actually mean?

This is the part people get wrong. Yield is the volume of mixed concrete the bag makes after you add water. It is not the volume of dry powder sitting in the bag, and it is not the size of the sack on the pallet.

Dry mix is loose. It has air between the sand, gravel, and cement. Once you add water and stir, the mix tightens up and the finished volume settles into a smaller, denser number. That finished number is the yield printed on the bag, and it is the only one that matters when you are filling a form.

So do not try to work backwards from the bag's physical size. Measure your hole or your slab, get a cubic foot number, and divide by the yield.

How many 80lb bags are in a cubic yard?

Forty-five. A cubic yard is 27 cubic feet, and each 80 lb bag makes 0.60 cubic feet. 27 divided by 0.60 gives you 45 bags.

That is a lot of mixing. Forty-five bags is roughly 3,600 pounds of material to haul, open, and turn by hand. Most people who hit that number stop and price a ready-mix truck instead. Bags make sense for posts, small pads, and repairs. Once you are past a yard, the math on your back stops working. Our pillar guide on how much concrete do I need walks through where that line usually falls.

How many cubic feet is a 60lb bag?

A 60 lb bag yields 0.45 cubic feet, which works out to 60 bags per cubic yard. It is the middle-of-the-road choice and the one a lot of DIYers land on.

Why pick 60 over 80? Weight. A 60 lb bag is easier to lift, easier to dump into a wheelbarrow without spilling half of it, and easier on your shoulders across a long afternoon. You need more bags to hit the same volume, but you will move them faster and hurt less the next day.

The 40 lb bag, at 0.30 cubic feet and 90 bags per yard, is the gentlest option. It is best for small patches and setting a couple of posts.

How do you convert cubic feet to bags?

One division. Take the cubic feet of concrete you need and divide it by the bag's yield.

Cubic feet needed / bag yield = number of bags

If your project is measured in cubic yards, multiply by 27 first to get cubic feet. Then divide. That is the whole method, and it works for any bag size on the chart above.

Worked example: a 10x10 slab at 4 inches

A 10 by 10 foot slab poured 4 inches thick comes out to 33.3 cubic feet. Divide 33.3 by 0.60 and you get 56 eighty-pound bags. That is before waste. We break this exact pour down step by step in our guide on how many bags of concrete for a 10x10 slab.

Worked example: a fence post hole

A typical fence post hole needs about 0.92 cubic feet of concrete around the post. Divide 0.92 by 0.60 and you get 2 eighty-pound bags per hole. Multiply by your post count and you have your pallet order.

Worked example: a 12 inch by 48 inch footing

A 12 inch diameter footing poured 48 inches deep holds 3.14 cubic feet. Divide 3.14 by 0.60 and you need 6 eighty-pound bags. Deck footings add up quickly once you count all of them.

Run your own numbers through the Concrete Calculator if your dimensions are anything other than these.

Why do bags of the same weight have different yields?

Because the mix is different. Two 80 lb bags from two brands can list slightly different yields, and a fast-setting mix will not match a standard mix even at the same weight.

The reason is aggregate. Different mixes use different sand and stone blends at different densities, so the same 80 pounds of material can occupy a slightly different finished volume. Fast-setting post mix, in particular, is formulated for a different job and often lists its own number.

The bag tells you. Every manufacturer prints the yield right on the packaging, usually near the mixing instructions. Read it before you buy in bulk. The 0.60, 0.45, 0.375, and 0.30 figures are the standard published yields and they are the right numbers to plan with, but confirm against the specific bag sitting in your cart.

How much extra concrete should you buy?

Add 5 to 10 percent, then round up. Always round up. You cannot buy 56.3 bags, and you cannot pause a pour to drive back to the store.

Where does the extra go? Sub-grade that is not perfectly level. Forms that bow out slightly under the load. Mix that ends up on the ground instead of in the hole. Spillage in the wheelbarrow. None of it is avoidable and all of it eats into your count.

On that 56 bag slab, a 10 percent cushion means buying about 62 bags. If you do not use them all, most stores take back unopened bags. That is a far better problem than a half-finished slab going stiff while you are stuck in the parking lot.

Bottom line

An 80 lb bag of concrete yields 0.60 cubic feet, a 60 lb bag yields 0.45, a 50 lb bag yields 0.375, and a 40 lb bag yields 0.30. That is 45, 60, 72, and 90 bags per cubic yard respectively, since a cubic yard is 27 cubic feet. Measure your project in cubic feet, divide by the yield, add 5 to 10 percent for waste, and round up. Confirm the yield printed on your specific bag before you order, then let the Concrete Calculator do the division for you.