Concrete calculator
Work out how much concrete you need in cubic yards, cubic feet or bags for slabs, footings, columns and more.
Concrete calculator
Work out how much concrete you need in cubic yards, cubic feet or bags for slabs, footings, columns and more.
Enter your dimensions to see the concrete estimate.
Volume needed
Project summary
How it works
These are volume estimates for planning purposes. Actual concrete requirements depend on form dimensions, waste and site conditions.
Concrete calculator
More than length times width
A rectangular slab is the simplest case, but concrete is poured in many shapes. Footings, columns, cylinders and stairs each have their own geometry, and getting the volume right for each one matters because concrete is ordered by the cubic yard and short loads carry a premium. This calculator handles the common shapes and gives you the volume, the bag count and the cost from the same inputs.
Why bags and cubic yards are different purchases
A cubic yard of ready-mix concrete is 27 cubic feet, delivered by truck and finished in one pour. Bags are sold at the hardware store, mixed by hand on site, and are the right choice for small jobs, repairs and anything a truck cannot reach. A standard 80-pound bag yields about 0.6 cubic feet, which means 45 bags make a cubic yard. The calculator shows both so you can compare.
The waste allowance matters more here than you think
Concrete waste comes from spillage, over-excavated forms, and the inevitable give and take of working with a material that sets in hours. Ten percent is a common allowance for slabs. For footings and columns, where the form is tight and the pour is controlled, five percent may be enough. For stairs, where the geometry is complex and the forms are fussy, fifteen percent is safer.
Frequently asked questions
How much concrete do I need for a 10 by 10 foot slab?
At 4 inches thick, a 10 by 10 foot slab is 33.3 cubic feet, which is about 1.23 cubic yards. With a 10 percent waste allowance, order 1.36 cubic yards, or round up to 1.5 cubic yards if your supplier sells in half-yard increments. In 80-pound bags, that is about 56 bags. Enter your own dimensions above for the exact figure.
How many bags of concrete make a cubic yard?
About 45 eighty-pound bags, or 60 sixty-pound bags. The math is exact: an 80-pound bag yields roughly 0.6 cubic feet, and 27 cubic feet make a cubic yard, so 27 divided by 0.6 is 45. A 60-pound bag yields about 0.45 cubic feet, which gives 60 bags per yard.
How many bags of concrete do I need for a 4 by 4 foot pad?
For a 4 inch thick pad that is 4 by 4 feet, you need about 0.2 cubic yards or roughly 10 bags of 60 pound concrete mix. The calculator gives you the exact number based on your dimensions and thickness.
How much does a cubic yard of concrete cost?
Ready mix concrete typically costs between 125 and 150 dollars per cubic yard delivered. Bags of dry mix cost more per cubic yard but are convenient for small jobs. The calculator shows cubic yards so you can price both options.
How long does concrete take to cure?
Concrete reaches about 70 percent of its full strength in 7 days and full strength at 28 days. You can walk on it after 24 to 48 hours. Keep it moist and covered for the first week to prevent cracking. The calculator gives you the volume, and your concrete supplier can advise on curing for your specific mix.
Do I need rebar in a concrete slab?
Rebar or wire mesh adds tensile strength and helps control cracking. Most slabs over 4 inches thick or slabs that bear loads benefit from reinforcement. The calculator focuses on concrete volume, but your structural requirements will determine whether you need rebar.
How thick should a concrete pad be?
A standard driveway is 4 to 6 inches thick. A patio or walkway is usually 4 inches. Heavy equipment pads may be 8 inches or more. The calculator lets you enter any thickness and shows the volume required.
Can I pour concrete myself?
Small slabs under 10 square yards are manageable for a skilled DIYer. Larger pours require experience with finishing, proper subgrade preparation and sometimes multiple trucks. The calculator gives you the volume, and your supplier can advise on the best delivery method for your project size.