Concrete Bag Calculator
A concrete bag calculator tells you how many pre-mix bags you need by dividing your pour volume by the yield of one bag. An 80 pound bag yields about 0.6 cubic feet, a 60 pound bag about 0.45, and a 40 pound bag about 0.30. Enter your dimensions and bag size below to get the exact bag count.
bag_size is a selector: 40lb, 50lb, 60lb, 80lb. Yields from CONCRETE_REFERENCES.
- Cubic feet
- 0
- Estimated cost
- $0.00
Enter your dimensions to see the result.
Estimate only. Material yields and prices vary by supplier and region; confirm before ordering.
How Many Bags of Concrete Do You Need?
To find how many bags of concrete you need, calculate your pour volume in cubic feet, then divide by the yield of your chosen bag size. An 80 pound bag yields about 0.6 cubic feet, so a 9 cubic foot pour needs 15 of them. Smaller bags yield less and need higher counts: the same pour takes 20 of the 60 pound bags or 30 of the 40 pound bags. The calculator compares bag sizes so you can pick the most practical option.
What Size Concrete Bags Should You Buy?
Bag size is a trade-off between handling and number of trips. The 80 pound bag is the most concrete-efficient and means fewer bags, but it is heavy to carry and mix. The 60 pound bag is a common middle ground, and 40 pound bags are easiest to handle but need many more. For anything beyond roughly half a cubic yard (about 45 of the 80 pound bags), ready-mix delivery is usually cheaper and far less work than bags.
When Should You Use Bags Instead of Ready-Mix?
Use bags for small projects: setting fence posts, a small pad, footings for a deck, or repairs. The practical ceiling is around half a cubic yard, because past that the number of bags, the mixing labor and the cost all climb faster than a ready-mix order would. Below that threshold, bags win on convenience and on avoiding ready-mix short-load fees. The calculator shows the bag count so you can judge where you fall.
Frequently asked questions
- How many 80lb bags of concrete make a yard?
- It takes 45 of the 80 pound bags to make one cubic yard, since each yields about 0.6 cubic feet and a yard is 27 cubic feet. For 60 pound bags it is 60 bags, and for 40 pound bags it is 90.
- How much does an 80lb bag of concrete cover?
- An 80 pound bag of pre-mix yields about 0.6 cubic feet of concrete. At 4 inches thick that covers roughly 1.8 square feet, so coverage drops as your slab gets thicker.
- How many bags of concrete for a fence post?
- A typical fence post hole takes 1 to 4 bags depending on hole size and post depth. The calculator sizes it precisely from your hole dimensions.