80 lb Bag of Concrete Coverage
One 80 lb bag of concrete mix makes 0.6 cubic feet of concrete. Spread at the standard 4 inch slab thickness, that covers 1.8 square feet. Coverage changes fast with thickness, so use the chart for the depth you are actually pouring.
Concrete Bag Calculator
Already know the yardage from a quote or a plan? Convert it straight to bags.
Rule of thumb: one cubic yard needs about 45 bags of 80 lb mix, 60 bags of 60 lb mix, or 90 bags of 40 lb mix.
What one 80 lb bag really covers
Coverage depends on thickness more than anything. This page charts one bag at every common thickness, plus bags per 100 square feet.
Every thickness charted
Coverage at 2, 3, 4, 5 and 6 inches, so you can read your slab straight off the chart.
Bags per 100 square feet
Planning a floor or a patio? The per 100 square feet counts turn an area into a bag order fast.
Based on the true yield
One 80 lb bag yields 0.6 cubic feet. Every coverage figure on this page is worked from that.
Converter included
Already know your yardage? Turn it into bags with the converter at the top of the page.
If you already know your yardage, the converter above turns it straight into 80 lb bags. If you are working from an area, the bags per 100 square feet column is the fastest way to estimate a whole slab.
80 lb bag of concrete coverage chart
| Thickness | Coverage per bag | Bags per 100 sq ft |
|---|---|---|
| 2 inches | 3.6 sq ft | 28 |
| 3 inches | 2.4 sq ft | 42 |
| 4 inches | 1.8 sq ft | 56 |
| 6 inches | 1.2 sq ft | 84 |
How coverage is calculated
Coverage = bag yield divided by thickness in feet. At 4 inches: 0.6 divided by 0.333 = 1.8 square feet per bag. Worked example, a 100 sq ft patio at 4 inches: 100 divided by 1.8 = 55.6, so 56 bags, before any waste allowance.
Frequently asked questions
How much area does one 80 lb bag cover at 4 inches?
1.8 square feet. That is why a modest 10 x 10 ft slab needs 62 bags once waste is included, even though the exact coverage math says 56.
How many 80 lb bags for 100 square feet?
At 4 inches thick, 56 bags before waste, and about 62 bags with a 10 percent allowance. At 6 inches, 84 bags before waste.
Does coverage change between brands?
For standard 80 lb concrete mix, the printed yield is 0.6 cubic feet across the major brands, so coverage is the same. Fast setting and specialty mixes can yield slightly less; check the bag.
Why is my real coverage less than the chart?
Uneven ground is the usual reason. A low spot just half an inch deeper over a wide area eats a lot of concrete, which is why orders add 5 to 10 percent.
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