Concrete Bag Calculator
How many bags of premixed concrete to buy for a small pour (pads, steps, footings or post holes) in 80, 60 and 40 lb sizes.
Bags = cubic feet ÷ bag yield: 0.6 cu ft for an 80 lb bag, 0.45 for 60 lb and 0.30 for 40 lb. One cubic yard takes 45 bags of 80 lb. A 4 × 4 ft pad 4 in thick is 5.3 cu ft: 9 bags of 80 lb or 12 of 60 lb, plus a bag spare.
Bags per cubic foot and yard
| Bag | Yield | Bags per cu yd | Bags for a 4 × 4 ft pad, 4 in |
|---|---|---|---|
| 80 lb | 0.6 cu ft | 45 | 9 |
| 60 lb | 0.45 cu ft | 60 | 12 |
| 40 lb | 0.3 cu ft | 90 | 18 |
Frequently asked questions
How many bags of concrete do I need?
Work out the volume in cubic feet (length × width × thickness in feet), add 10%, and divide by the bag yield: 0.6 cu ft per 80 lb bag, 0.45 per 60 lb and 0.30 per 40 lb.
How many 80 lb bags of concrete make a yard?
About 45 bags (27 cu ft ÷ 0.6 cu ft per bag).
How many 60 lb bags of concrete make a yard?
About 60 bags.
How much area does an 80 lb bag of concrete cover?
About 1.8 sq ft at 4 in thick, or 3.6 sq ft at 2 in.
Should I buy 60 or 80 lb bags?
The concrete is the same; 80 lb bags are cheaper per cubic foot but heavier to lift. 60 lb bags are easier to carry and mix.
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Volumes: slabs and footings length × width × depth; columns π r² h; steps width × run × rise × n(n+1) ÷ 2. Bag yields from premixed concrete labels (80 lb 0.6 cu ft, 60 lb 0.45, 40 lb 0.30). Fresh concrete weighs about 4,050 lb per cu yd. Typical thickness: 4 in for patios and walks, 5–6 in for driveways and heavier loads. Rebar laps of about 18 in; welded wire 5 × 10 ft sheets. Structural work must follow your local code.