Bag calculator
Concrete Bag Calculator
Calculate how many bags of concrete you need for your project. Supports 40lb, 50lb, 60lb, and 80lb bags with instant volume and cost estimates.
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How Many Bags of Concrete Do You Need?
Calculating bag count is simple once you know your total volume. Each bag size yields a different amount of mixed concrete:
- 40 lb bag: yields ~0.30 cubic feet
- 50 lb bag: yields ~0.375 cubic feet
- 60 lb bag: yields ~0.45 cubic feet
- 80 lb bag: yields ~0.60 cubic feet
Divide your total cubic feet (including waste factor) by the bag yield to get your bag count. Always round up to ensure you have enough concrete to complete your project.
When to Use Bagged Concrete
Bagged concrete is ideal for small projects under 1 cubic yard. It's convenient, requires no special equipment, and you can mix only what you need. Common uses include:
- Setting fence posts and deck posts
- Small patio patches and repairs
- Anchor bolts and small footings
- Walkway sections under 10 square feet
Cost Comparison: Bags vs Ready-Mix
For projects under 1 cubic yard, bagged concrete is often more cost-effective when you factor in delivery fees for ready-mix. For larger projects, ready-mix delivery is usually cheaper per cubic yard and ensures consistent quality across your entire pour.
Frequently Asked Questions
How many 80lb bags of concrete in a yard?
One cubic yard equals 27 cubic feet. Since an 80lb bag yields 0.60 cubic feet, you need approximately 45 bags per cubic yard (27 ÷ 0.60 = 45).
How many bags for a 4x4 post hole?
A 12-inch-diameter post hole that is 3 feet deep holds about 2.36 cubic feet. With 80 lb bags yielding about 0.60 cubic feet each, you need 4 bags before waste or 5 bags with a 10% allowance.
Is it cheaper to mix your own concrete?
For small projects, bagged concrete is convenient and cost-effective. For larger projects (over 1 yard), ready-mix delivery is usually cheaper per cubic yard and saves significant labor time.
How long does bagged concrete last?
Unopened bags last 6-12 months when stored in a dry location. Once mixed, concrete should be placed within 20-30 minutes before it begins to set.