Concrete Bags Calculator
Enter your project dimensions and this concrete bags calculator returns the exact number of bags you need in 40, 60 and 80 pound sizes, along with the volume in cubic feet and cubic yards and a cost estimate. It works for slabs, footings, post holes and tube forms, and the counts match Quikrete, Sakrete and store brand mixes.
Concrete Bags Calculator
Start from the shape you can measure, not from a volume you have to guess. The tool works out the volume first, then divides by the yield of the bag you choose. A fractional bag is not something you can buy, so it rounds up and shows a waste buffer on top.
How to calculate how many bags of concrete you need
The method has two steps. First find the volume. For a slab or footing, multiply length times width times thickness. For a round post hole or tube, use pi times the radius squared times the depth. Then divide the volume by the yield of one bag.
The yields come from the Quikrete Concrete Mix data sheet and hold across compliant brands, since bags are rated by the volume of wet mix they produce.
| Bag size | Yield per bag | Bags per cubic yard | Bags per cubic foot |
|---|---|---|---|
| 40 lb | 0.30 cu ft | 90 | 3.3 |
| 50 lb | 0.375 cu ft | 72 | 2.7 |
| 60 lb | 0.45 cu ft | 60 | 2.2 |
| 80 lb | 0.60 cu ft | 45 | 1.7 |
Worked example, a 10 by 10 shed pad
Set the type to slab and enter 10 feet by 10 feet by 4 inches. Convert the thickness: 4 divided by 12 is 0.333 feet. The volume is 10 times 10 times 0.333, or 33.3 cubic feet. Divide by the 80 pound yield of 0.60 and you get 56 bags. In 60 pound bags it is 74. Add a 10 percent buffer for spillage and uneven base and you would buy about 62 bags of 80 pound mix. At 56 bags, that is more than a ton and a half of material to haul and mix, so this size sits right at the edge where a short load delivery makes sense.
How much water each bag needs
Water controls both yield and strength. Too little and the mix will not reach its rated volume or bond well. Too much raises the water to cement ratio, which lowers strength and causes shrinkage cracks. The Quikrete data sheet lists about 6 to 9 pints for an 80 pound bag, scaling down with bag size. Aim for a uniform, plastic mix that holds its shape, not a soupy one that seems to stretch further.
Bags on a pallet
Pallet quantity is set by weight, around 3,000 to 3,360 pounds. A standard pallet is about 42 bags of 80 pound mix, 56 bags of 60 pound, or 80 bags of 40 pound. A pallet of 80 pound bags is roughly 0.9 cubic yards, which is another sign that a job near a full pallet is worth pricing against ready mix.
A note on brands and bag sizes
Quikrete and Sakrete standard concrete mixes share the same yields, so the counts here apply to either, and to store brands sold at Home Depot, Lowe’s and Menards. Watch two exceptions. Fast setting products often ship as 50 pound bags with their own yield, so a post job costed on 60 pound math will be off. High strength and crack resistant blends can run slightly under. In much of South Asia the common 50 kilogram bag is cement, not bagged concrete, so a bag count from this tool does not apply there. Whatever you buy, read the yield printed on the bag and rerun the count if it differs.
Mistakes that throw off a bag count
- Leaving thickness in inches on a field set to feet. A 4 inch slab entered as “4” asks for a 4 foot slab and returns a count twelve times too high.
- Typing a radius where the tool asks for diameter. The radius is squared, so this changes a cylinder count four times over.
- Ordering the exact figure with no buffer. Bags are sold whole, and a short pour cannot be patched cleanly once it sets.
- Using the gross hole volume for posts without subtracting the post. The post takes up part of the hole, though on hand dug holes the extra often covers over cut.
Related calculators
- Slab calculator for flatwork volume and reinforcement
- Column calculator for piers, sonotubes and posts
- Footing calculator for strip and pier footings
- How to calculate concrete guide for formulas and worked examples
Frequently asked questions
How many bags of concrete do I need?
Find your volume in cubic feet, then divide by the bag yield: 0.60 for 80 pound, 0.45 for 60 pound, 0.30 for 40 pound. Round up and add 5 to 10 percent. The tool does this once you enter the dimensions.
How many bags of concrete are in a cubic yard?
About 45 bags of 80 pound mix, 60 bags of 60 pound, or 90 bags of 40 pound, since one cubic yard is 27 cubic feet.
How many cubic feet are in an 80 pound bag of concrete?
An 80 pound bag yields about 0.60 cubic feet. A 60 pound bag yields 0.45, and a 40 pound bag yields 0.30, per the manufacturer data sheet.
How many 80 pound bags make a cubic yard?
About 45, found by dividing 27 cubic feet by 0.60 cubic feet per bag.
How many bags of concrete are on a pallet?
Around 42 bags of 80 pound, 56 of 60 pound, or 80 of 40 pound, set by a pallet weight near 3,000 to 3,360 pounds.
When is bagged concrete cheaper than ready mix?
Bags win under about one cubic yard, roughly 45 bags of 80 pound mix. Above that, ready mix is usually cheaper per yard and saves hours of mixing.
How much water does an 80 pound bag need?
About 6 to 9 pints, following the figure printed on the bag. Mix to a uniform, plastic consistency rather than adding water by eye.
Do Quikrete and Sakrete bags use the same count?
Yes for standard concrete mix, since both share the same yields. Fast setting and specialty lines can differ, so check the bag.
References
- Quikrete, Concrete Mix 1101 data sheet (yields and water per bag): https://www.quikrete.com/PDFs/DATA_SHEET-Concrete Mix 1101.pdf
- Sakrete product information: https://www.sakrete.com/products
- ASTM C387, Standard Specification for Packaged, Dry, Combined Materials for Concrete: https://www.astm.org/c0387_c0387m-17.html
- Portland Cement Association, concrete technology library: https://cement.org
Methodology: volume is derived from the shape you enter, then divided by published manufacturer bag yields and rounded up to whole bags, with waste buffers added. Yields are approximate compacted figures; a hand mixed batch may place slightly less. Read the yield on your product and verify structural work with a licensed engineer. Recommended: attribute this page to a named author and add a review date.