Quikrete Cubic Feet Per Bag: Sizes & Coverage

This calculator works out how many cubic feet of concrete are in a Quikrete bag based on its weight, and it also tells you the volume in cubic yards and the number of 60-lb and 80-lb bags you would need for a given project volume. You enter the bag weight in pounds (or the total project volume in cubic feet), and the calculator returns the bag’s volume and the bags required. The standard rule is that a 60-lb bag yields about 0.45 cubic feet and an 80-lb bag yields about 0.60 cubic feet, but the exact figure depends on the specific mix.

Formula

The volume of concrete in a bag is found by dividing the bag’s weight by the density of the cured concrete mix. The industry-standard density for Quikrete concrete mixes is approximately 133 lb per cubic foot.

Volume per bag (cu ft) = Bag weight (lb) ÷ 133 (lb/cu ft)

Where:

• Bag weight – the labeled weight of the dry mix in pounds (e.g., 40, 60, 80).
• 133 lb/cu ft – the average density of Quikrete concrete after mixing and curing.

For a project, the number of bags is:

Bags needed = Project volume (cu ft) ÷ Volume per bag (cu ft)

Worked Example

Using the default values from the calculator (an 80-lb bag and a 2-cubic-foot project):

1. Volume per bag = 80 lb ÷ 133 lb/cu ft = 0.6015 cu ft (rounded to 0.602 cu ft).
2. Bags needed = 2 cu ft ÷ 0.6015 cu ft = 3.32 bags, so you would need to buy 4 bags.
3. Volume per bag in cubic yards = 0.6015 ÷ 27 = 0.0223 cu yd.

The calculator shows 0.602 cu ft for the bag volume and 3.3 bags for the 2-cubic-foot project, matching this calculation.

Why Bag Volume Varies by Mix

Not all Quikrete products have the same density. The 133 lb/cu ft figure is a general average for standard concrete mixes. Some products are lighter or heavier:

• Standard concrete mix – about 133 lb/cu ft (yields 0.45 cu ft per 60-lb bag, 0.60 cu ft per 80-lb bag).
• Sand mix or mortar mix – slightly denser, around 140 lb/cu ft, so a 60-lb bag yields about 0.43 cu ft.
• Lightweight concrete – can be as low as 100 lb/cu ft, giving more volume per pound.
• Fast-setting concrete – similar density to standard mix but may contain additives that affect volume slightly.

Always check the bag label for the exact yield. Quikrete prints the cubic-foot yield on the side of every bag, usually in the “Coverage” section. For example, an 80-lb bag of standard concrete mix states “0.60 cu ft” directly.

How to Use the Calculator for Real Projects

To get accurate bag counts for a slab, footing, or post hole, follow these steps:

1. Measure the project dimensions in feet (length × width × depth for a slab; for a round hole, use π × radius² × depth).
2. Convert all measurements to feet (e.g., 4 inches = 4/12 = 0.333 ft).
3. Multiply to get the volume in cubic feet.
4. Enter that number in the calculator’s “Project volume” field.
5. Adjust the bag weight to match what you plan to buy (60 or 80 lb are most common).
6. Read the “Bags needed” result – always round up to the nearest whole bag.

For example, a 10 ft × 10 ft slab that is 4 inches thick has a volume of 10 × 10 × 0.333 = 33.3 cu ft. With 80-lb bags (0.60 cu ft each), you need 33.3 ÷ 0.60 = 55.5 bags, so buy 56 bags.

Common Mistakes and Misconceptions

One frequent error is confusing cubic feet with cubic yards. Ready-mix concrete is ordered by the cubic yard (27 cu ft), but bagged concrete is sold by the cubic foot. A common misconception is that a 60-lb bag equals 1 cubic foot – it does not; it is about 0.45 cu ft. Another mistake is using the dry volume instead of the wet volume. The bag yield already accounts for the fact that water reduces the volume when mixed, so you should not add extra for shrinkage.

Rounding errors also cause problems. If you are pouring a small slab and the calculator says 3.32 bags, buying 3 bags will leave you short. Always round up to the next whole bag. For large projects, it is wise to add 5–10% extra to cover spillage, uneven subgrades, or slight measurement errors.

Comparing Bag Sizes: 40 vs 60 vs 80 lb

Quikrete is commonly sold in 40-lb, 60-lb, and 80-lb bags. Here is how they compare for standard concrete mix:

• 40-lb bag – yields about 0.30 cu ft (0.011 cu yd). Good for small repairs, stepping stones, or filling narrow post holes.
• 60-lb bag – yields about 0.45 cu ft (0.017 cu yd). The most popular size for medium projects like fence posts or small pads.
• 80-lb bag – yields about 0.60 cu ft (0.022 cu yd). Best for larger slabs, footings, and when you want fewer bags to handle.

For a 1-cubic-foot project, you would need 2 of the 40-lb bags, 2.22 of the 60-lb bags (so 3), or 1.67 of the 80-lb bags (so 2). The 80-lb bags are usually the most economical per cubic foot, but they are heavy to carry and mix.

Cost and Practical Considerations

Bagged concrete costs more per cubic foot than ready-mix from a truck, but it is the only option for small jobs, remote locations, or when you need to mix in stages. As a rough guide, a 60-lb bag typically costs between $4 and $7, and an 80-lb bag between $5 and $9, but prices vary by region and store. For a 1-cubic-yard project (27 cu ft), you would need about 45 of the 80-lb bags or 60 of the 60-lb bags. That is a lot of mixing – many people rent a small mixer for anything over 10 bags.

Also consider the physical effort: an 80-lb bag of dry mix weighs 80 lb, and when mixed with water it becomes even heavier. If you have back problems or limited help, choose 60-lb bags. For large pours, it may be cheaper to order a ready-mix truck, but only if the truck can reach the site.

Safety and Mixing Tips

Concrete dust is harmful if inhaled, and wet concrete can cause skin burns. Always wear a dust mask, safety glasses, and waterproof gloves when mixing. Work in a well-ventilated area. When mixing, add water gradually – Quikrete recommends about 3 quarts of water per 80-lb bag, but the exact amount is on the bag. The mix should be plastic but not soupy. If it is too dry, it will not cure properly; too wet, it will be weak. Dispose of any leftover wet concrete in a trash bag and let it harden before putting it in the bin – never pour it down drains.

Frequently Asked Questions

How many cubic feet are in a 60-lb bag of Quikrete?

A 60-lb bag of standard Quikrete concrete mix yields about 0.45 cubic feet (0.017 cubic yards). This is the most common size for fence posts and small slabs. The exact yield is printed on the bag; some specialty mixes like sand mix yield slightly less (about 0.43 cu ft).

How many 80-lb bags of Quikrete do I need for 1 cubic yard?

One cubic yard equals 27 cubic feet. Since an 80-lb bag yields 0.60 cubic feet, you need 27 ÷ 0.60 = 45 bags. That is 3,600 lb of dry mix, which is a substantial amount – you would likely want to rent a mixer or order ready-mix for that volume.

Does the calculator work for all Quikrete products?

It works for any product with a density near 133 lb/cu ft, which covers standard concrete, fast-setting concrete, and high-strength mixes. For lighter products like lightweight concrete or heavier ones like sand mix, the yield per bag differs. Check the bag label for the exact cubic-foot yield and adjust the bag weight in the calculator if needed.

Why does the bag say “0.45 cu ft” but I get less when I mix it?

The labeled yield is the volume of the cured concrete, not the dry powder. When you add water, the mix shrinks slightly. If you measure the dry powder, it will appear to be more than 0.45 cu ft, but after mixing and settling, the volume matches the label. Do not add extra mix to compensate – follow the water instructions.

Can I use the calculator for mortar or sand mix?

Yes, but the density will be different. Mortar mix and sand mix are denser (around 140 lb/cu ft), so a 60-lb bag yields about 0.43 cu ft instead of 0.45. For accurate results, use the bag’s stated yield. The calculator’s 133 lb/cu ft is a good average for standard concrete, but not for all Quikrete products.

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in w | Bag weight | lb | 80 | 0
in v | Project volume | cu ft | 2 | 0
out bag_vol | Volume per bag | cu ft | w / 133 | 3
out bags | Bags needed | bags | v / (w / 133) | 1
out bag_vol_yd | Volume per bag | cu yd | (w / 133) / 27 | 4