Concrete Bag Calculator
If you already know the volume — from plans, a supplier quote or the main calculator — this page turns it straight into bag counts for every standard premix size.
The short answer: divide the volume in cubic feet by the bag’s yield and round up. One cubic yard (27 ft³) is 45 bags of 80 lb, 60 bags of 60 lb, 72 bags of 50 lb or 90 bags of 40 lb. Add 10% for waste before you order.
Working from dimensions instead? The main concrete calculator handles slabs, footings, columns and steps.
Bag counts by the yard
Exact counts with no waste allowance, so you can see the raw conversion before margins:
| Volume | 80 lb bags | 60 lb bags | 50 lb bags | 40 lb bags |
|---|---|---|---|---|
| 1 yd³ (27 ft³) | 45 | 60 | 72 | 90 |
| 2 yd³ (54 ft³) | 90 | 120 | 144 | 180 |
| 3 yd³ (81 ft³) | 135 | 180 | 216 | 270 |
| 4 yd³ (108 ft³) | 180 | 240 | 288 | 360 |
| 5 yd³ (135 ft³) | 225 | 300 | 360 | 450 |
How bag math works
Bags are sold by weight but concrete is placed by volume, so the bridge between them is the yield printed on the bag: the cubic feet of mixed, placed concrete one bag produces. Standard premix yields are 0.60 ft³ for an 80 lb bag, 0.45 ft³ for 60 lb, 0.375 ft³ for 50 lb and 0.30 ft³ for 40 lb. Bags needed = volume ÷ yield, always rounded up. The full per-yard table lives on our bags per yard page.
Weight matters too: a yard in 80 lb bags is 45 bags and roughly 3,600 lb of dry mix to move — before water. If the total weight column above looks like a workout, that’s the calculator telling you to price a ready-mix truck on the cost page.
Frequently asked questions
How many 80 lb bags make a cubic yard?
45 bags. Each 80 lb bag yields about 0.60 ft³, and a cubic yard is 27 ft³: 27 ÷ 0.60 = 45 exactly, before any waste allowance.
Should the waste allowance apply to bags too?
Yes. The shortfall waste covers — spillage, uneven ground, over-excavation — happens whether the concrete comes from a truck or a bag. Ten percent is the standard planning figure.
My bag brand shows a different yield. Which number wins?
The label on your bag. Yields here are the standard figures major manufacturers print, but a few brands differ by a hundredth or two of a cubic foot. On a big pour that difference is a bag or two either way.
Can I mix bag sizes on one pour?
You can — the volumes simply add. Just total the yield of what you have (bags × their yield) and compare it with the waste-adjusted volume you need.