Calculator
Plotly Graph
The graph shows how bag count converts into cubic yards for the selected bag size.
Example Data Table
| Bag Size | Approx. Yield per Bag | Bags per Cubic Yard | Approx. Bags for 0.5 yd³ | Approx. Bags for 1.0 yd³ |
|---|---|---|---|---|
| 40 lb | 0.30 ft³ | 90 | 45 | 90 |
| 60 lb | 0.45 ft³ | 60 | 30 | 60 |
| 80 lb | 0.60 ft³ | 45 | 23 | 45 |
Half-yard bag counts are rounded to practical purchase values.
Formula Used
Cubic feet = Number of bags × Yield per bag
Cubic yards = Cubic feet ÷ 27
Adjusted volume = Base volume × (1 + Waste% ÷ 100)
Bags required = Adjusted cubic yards × Bags per cubic yard
Cubic feet = Length × Width × (Depth in inches ÷ 12)
This calculator uses common approximate yields: 40 lb = 0.30 ft³, 60 lb = 0.45 ft³, and 80 lb = 0.60 ft³.
How to Use This Calculator
- Select the mode that matches your task.
- Choose 40 lb, 60 lb, or 80 lb bags.
- Enter bag count, target yards, or slab dimensions.
- Add waste percentage for spill, grade loss, or overage.
- Enter price per bag to estimate material cost.
- Press Calculate to view results above the form.
- Use the CSV or PDF buttons to save results.
FAQs
1) How many 80 lb bags make one cubic yard?
About 45 bags. That estimate assumes each 80 lb bag yields roughly 0.60 cubic feet of mixed concrete. Always round up for real purchases.
2) How many 60 lb bags make one cubic yard?
About 60 bags. This comes from a typical 0.45 cubic foot yield per 60 lb bag. Site conditions and mix variations can change actual output slightly.
3) How many 40 lb bags make one cubic yard?
About 90 bags. That uses an approximate yield of 0.30 cubic feet per bag. Small bags are convenient, but many more are needed.
4) Why should I include waste percentage?
Waste covers spillage, uneven subgrade, form leakage, and mixing loss. Adding 5% to 10% often prevents under-ordering on practical concrete jobs.
5) Can I estimate bags from slab dimensions?
Yes. Enter the slab length, width, and depth. The calculator converts dimensions into volume, then estimates the exact and rounded bag count.
6) Are the bag yields exact for every brand?
No. Published yields vary slightly by brand, aggregate content, and water added. Manufacturer instructions should always override generic estimates when available.
7) Should I buy the exact bag count shown?
Usually no. Buy the rounded-up count. Concrete shortages slow a pour, so extra bags are safer than finishing short during placement.
8) Does this replace engineer or project specifications?
No. It is a planning tool. Use it for estimating only, then confirm mix type, thickness, reinforcement, and quantity with project documents.