What this calculates
Bagged premix is convenient for small jobs. This tool converts your project volume into a whole number of bags for the selected size and editable product yield, rounding up so you are not short.
Preset yields are examples, not universal specifications. Enter the mixed yield on your product label; bag weight alone does not establish yield.
Formula
Bags = total volume (cu ft) ÷ bag yield (cu ft), rounded up
Typical yields: 40 lb ≈ 0.30 cu ft · 60 lb ≈ 0.45 cu ft · 80 lb ≈ 0.60 cu ft
Worked example
4 × 4 ft pad, 4 in thick
- 1.4 × 4 × 0.333 = 5.33 cu ft
- 2.Add 10% waste: 5.87 cu ft
- 3.80 lb: 5.87 ÷ 0.60 = 9.8 → 10 bags · 60 lb: 14 bags · 40 lb: 20 bags
Common mistakes
- Assuming every brand yields the same — fast-setting and high-strength mixes can differ.
- Using bags for large pours. Above roughly a cubic yard, mixing 45+ bags by hand is slow and ready-mix is usually more practical.
- Forgetting water, a mixer and enough helpers to place the concrete before it sets.
Frequently asked questions
How many 80 lb bags make a cubic yard?
At about 0.60 cu ft per bag, one cubic yard (27 cu ft) takes 45 bags of 80 lb premix.
How many 60 lb bags make a cubic yard?
At roughly 0.45 cu ft per bag, a cubic yard takes about 60 bags of 60 lb premix.
Is it cheaper to use bags or ready-mix?
For very small jobs bags usually win. For larger pours, ready-mix tends to be cheaper per yard, though delivery minimums and short-load fees apply. Compare quotes with the cost calculator.