Concrete bags
How many bags of concrete do I need? The answer starts with your slab dimensions. This concrete bags calculator compares the 60 lb and 80 lb bag counts side by side for the same slab. The 60 lb bag is easier to carry; the 80 lb bag delivers more volume per bag.
Concrete bags
Tap or type into any yellow number on the drawing to change it.
Avg US retail price, checked Aug 2026.
An 80 lb bag yields 0.6 cubic feet of concrete, while a 60 lb bag yields 0.45 cubic feet. For a given slab volume, the larger bag delivers more material per bag, so the calculator typically shows a higher 60 lb bag count and a lower 80 lb bag count. Both counts include a 10% waste factor, so you buy extra concrete to allow for spills, uneven ground, and off-cuts. An average price is listed only for the 80 lb bag; as of the August 2026 check, the price line appears beside that bag only, and the 60 lb bag count has no cost line. The results include the cubic yard figure, useful if you are comparing against ready-mix delivery.
The calculator asks for length, width, and thickness in feet and inches on the imperial side; on the metric side it uses meters and centimeters.
Which bag size should I choose: 60 lb or 80 lb?
Choose based on how much weight you want to carry and how many bags you are willing to handle. The 60 lb bag is lighter to lift, while the 80 lb bag yields 0.6 cu ft per bag versus 0.45 cu ft for the 60 lb bag, so for the same slab you will need fewer 80 lb bags. Both counts are shown after you enter your dimensions.
Why does the 60 lb bag have no price listed?
The average price on this page is for the 80 lb bag only, checked Aug 2026. The 60 lb bag count is shown without a cost line because no average price has been provided for that size.
How does the 10 percent waste factor change the 60 lb and 80 lb bag counts?
A 10% waste factor is added to the calculated slab volume before the bag count is determined. The extra material covers spills, uneven ground, and off-cuts, and it is applied equally to the 60 lb and 80 lb counts.