How many bags of concrete do I need for a 10x10 slab?
At 4 inches thick, a 10 × 10 slab needs about 33.3 cubic feet. With 10% waste, that is roughly 62 of the 80 lb bags, 82 of the 60 lb bags, or 123 of the 40 lb bags.
Bag count estimator
Concrete Bag Calculator
100% Free — No Sign Up Required
Calculate how many bags of concrete you need. Enter your project dimensions and compare 40 lb, 60 lb, and 80 lb bag counts instantly.
Cubic yards
2.44
Cubic feet
66.00
Cubic meters
1.87
Estimated bags
110
Includes a 10% waste factor. This estimate is for planning only; forms, subgrade and delivery conditions can change the final order.
Quick Cost Estimate
Estimated total cost
$715.00
Quick Cost Estimate multiplies the estimated bag count by your bag price. It excludes tax, delivery and tools.
How the Concrete Bag Calculator Works
To calculate concrete bags, the tool first works out the project volume from your length, width, and depth, applies the waste factor, and then divides the adjusted cubic feet by the yield of the bag size you selected. The answer to "how many bags of concrete do I need" always rounds up, because partial bags cannot be purchased and rounding down leaves the pour short. Typical yields are about 0.30 cubic feet for a 40 lb bag, 0.45 cubic feet for a 60 lb bag, and 0.60 cubic feet for an 80 lb bag. Switch between bag sizes at any time — the bag concrete calculator recalculates instantly, so you can compare how many trips, lifts, and mixes each option means before you head to the store.
40 lb vs 60 lb vs 80 lb Bags
The three common bag sizes trade weight against coverage. An 80 lb bag yields the most concrete per bag and per dollar, but each bag is a heavy lift and a full mix in a wheelbarrow. A 60 lb bag is the middle ground that most people can handle repeatedly. A 40 lb bag is the easiest to carry and mix by hand, but a given project needs twice as many of them as 80 lb bags. In coverage terms, one cubic yard of concrete takes about 90 of the 40 lb bags, 60 of the 60 lb bags, or 45 of the 80 lb bags. For a concrete calculator bags comparison on a real project: a 4-inch-thick 6 × 6 ft pad needs roughly 12 cubic feet of concrete, which is about 40 bags at 40 lb, 27 bags at 60 lb, or 20 bags at 80 lb before waste.
Quikrete, Sakrete, and Generic Mixes
The default yields in this calculator match the published numbers for the major brands: Quikrete and Sakrete both rate their standard concrete mix at approximately 0.60 cubic feet per 80 lb bag, 0.45 cubic feet per 60 lb bag, and 0.30 cubic feet per 40 lb bag, and most store-brand mixes are formulated to the same yields. Specialty products differ — fast-setting, high-strength, and crack-resistant mixes can yield slightly more or less per bag — so when the count is tight, check the yield printed on the bag you actually buy and compare it against the estimate. Water ratio matters too: over-watering stretches the volume slightly but weakens the cured concrete, so follow the bag directions rather than chasing extra yield.
From Area to Bags — and When to Switch to Ready Mix
If you already know the area you need to cover, the reverse calculation is straightforward: multiply the area in square feet by the thickness in feet to get cubic feet, then divide by the bag yield. A 50 sq ft walkway at 4 inches is 50 × 0.333 = 16.7 cubic feet, or about 28 of the 80 lb bags. As bag counts climb, mixing becomes the bottleneck — beyond roughly 40 to 50 bags, a ready mix delivery measured with the concrete yard calculator is usually faster and more consistent, and for a full slab the concrete slab calculator gives thickness guidance too. The quick cost field below the results is a material-only check: enter your price per bag and it multiplies the estimated bag count into a total before tax, delivery, or tools.
Concrete Calculators by Project Type
Concrete Slab Calculator
Use length, width and thickness for floors, patios and rectangular slabs.
Concrete Pad CalculatorEstimate square, rectangular or circular pads with a quick cost field.
Concrete Yard CalculatorConvert dimensions into cubic yards, cubic feet and cubic meters.
Concrete Bag CalculatorEstimate 40 lb, 60 lb and 80 lb bags after waste is added.
Frequently Asked Questions
How much does an 80 lb bag of concrete yield?
About 0.60 cubic feet per bag for standard Quikrete or Sakrete mix. Always check the yield printed on the specific product you buy.
How many 80 lb bags make a cubic yard?
About 45 bags. One cubic yard is 27 cubic feet, and each 80 lb bag yields roughly 0.60 cubic feet.
Why does the bag count round up?
Concrete bags are sold as whole bags, and rounding down would leave the project short. The calculator always rounds up after applying waste.