Free Concrete Bag Calculator
Use this concrete bag calculator to see how many bags of concrete mix to buy, in every common bag size.
Already know the volume?
Numbers can't be negative.
| 40 lb bags | 37 |
| 50 lb bags | 30 |
| 60 lb bags | 25 |
| 80 lb bags | 19 |
Bagged concrete mix is sold by weight, but what matters is how much concrete each bag makes. A typical 80 lb bag yields about 0.60 cubic feet, a 60 lb bag about 0.45, a 50 lb bag about 0.375 and a 40 lb bag about 0.30.
Enter your slab or pad below to see the bag count for every size at once, or type a volume you already know into the converter under the calculator.
How many bags of concrete do I need? An example
A 6 × 4 ft pad, 4 in thick: 24 sq ft × 4 in ÷ 12 = 8 cu ft, plus 10% extra = 8.8 cu ft. Divide by 27 to get 0.33 cubic yards, which weighs about 0.65 tons, or 15 × 80 lb bags (0.60 cu ft).
How deep should concrete be?
| Use | Thickness | Notes |
|---|---|---|
| Small pad or step | 3 to 4 in | |
| Walkway, patio or shed base | 4 in | |
| Driveway or heavier loads | 5 to 6 in | At this size, ready-mix is usually easier than bags. |
Bag yields and bags per cubic yard
| Bag size | Yield (cu ft) | Bags per cu yd | Bags per 10 sq ft at 4 in | Weight to carry per cu yd |
|---|---|---|---|---|
| 40 lb | 0.30 | 90 | 12 | 3,600 lb |
| 50 lb | 0.375 | 72 | 9 | 3,600 lb |
| 60 lb | 0.45 | 60 | 8 | 3,600 lb |
| 80 lb | 0.60 | 45 | 6 | 3,600 lb |
Bags of concrete per cubic yard
| Bag | Yield | Bags per cubic yard |
|---|---|---|
| 40 lb bag | 0.3 cu ft | 90 |
| 50 lb bag | 0.375 cu ft | 72 |
| 60 lb bag | 0.45 cu ft | 60 |
| 80 lb bag | 0.6 cu ft | 45 |
Buying tips
- Bigger bags mean fewer trips but heavier lifting: 45 bags of 80 lb make one cubic yard and weigh 3,600 lb in total.
- Above about 1 cubic yard (45 bags of 80 lb), ready-mix delivery is usually cheaper and much less work. Use the concrete calculator for ready-mix orders.
- Fast-setting mixes used for fence posts often yield less per bag than standard mix. Use the yield printed on the bag.
- Buy one or two extra bags. Returning an unopened bag is easier than stopping halfway through a pour.
How much does concrete weigh?
A cubic yard of concrete typically weighs 3,800 to 4,200 lb (1.9 to 2.1 tons). The calculator uses 4,000 lb (2 tons) per cubic yard. Moisture and grading change the weight, so if your supplier sells by the ton, ask for their figure.
Frequently asked questions
How many bags of concrete do I need?
Work out the volume in cubic feet (length × width × thickness in feet), add about 10%, then divide by the bag yield. For a 6 × 4 ft pad 4 in thick: 8 cu ft + 10% = 8.8 cu ft, which is 15 bags of 80 lb or 20 bags of 60 lb.
How many 80 lb bags of concrete are in a yard?
About 45. A cubic yard is 27 cubic feet and an 80 lb bag makes about 0.60 cubic feet.
How many 60 lb bags of concrete make a yard?
About 60, at 0.45 cubic feet per bag.
Bagged concrete or ready-mix?
Bagged concrete makes sense up to about 1 cubic yard. Above that, ready-mix delivery is usually cheaper and far less work than mixing 45+ bags.
Is this a cement bag calculator?
Yes, for the bagged concrete mix most people mean. Bags of plain Portland cement are different: they must be mixed with sand and gravel, so the yield depends on your mix recipe.
Can I use it as a Quikrete calculator?
Yes. Quikrete, Sakrete and other brands sell 40, 50, 60 and 80 lb bags with similar yields. We are not affiliated with any brand; check the yield printed on your bag.
How accurate is this concrete bag calculator?
The concrete bag calculator gives the exact volume for the measurements you enter, then adds 10% extra (you can change it). Weights use a typical 2 tons per cubic yard; real loads vary with moisture, so confirm with your supplier if you buy by the ton. Measure carefully: an error of one inch in depth changes a 3 inch layer by a third.
How the concrete bag calculator works
Volume = area × thickness. Each area is worked out from its shape (length × width, π × radius², or ½ × base × height), converted to square feet, multiplied by the thickness in feet, and added up. Cubic feet ÷ 27 = cubic yards.The extra percentage is then added, and bag counts are rounded up to whole bags. See how we calculate for every figure we use.