Concrete Calculator: Bags, Cubic Yards and Cost

HOW IT WORKS

Concrete volume, bags and ready-mix

Choose the shape that best matches your pour, enter the dimensions, then add an optional waste allowance. The calculator shows cubic feet, cubic yards and cubic meters, so you can use the same result for bagged concrete or a ready-mix quote.

Preset concrete bag yields

The preset 40, 50, 60, 80 and 90 lb bag yields follow the current QUIKRETE Concrete Mix No. 1101 data sheet: approximately 0.30, 0.375, 0.45, 0.60 and 0.675 cubic feet per bag respectively. Products from another brand or a high-yield mix can differ, so use the custom-yield option when the bag label gives a different number.

Slabs, walls, post holes and solid stairs

Slabs and rectangular footings use length × width × thickness. Walls use length × height × thickness. Round post holes and columns use π × radius² × height or depth. The stair option estimates a solid stepped shape using stair width, tread depth, riser height and number of steps; landings, voids and special structural geometry are not included.

Bagged concrete vs ready-mix

Bagged concrete can be convenient for smaller pours, while ready-mix may be more practical for larger jobs. Delivery minimums, short-load fees and local pricing vary by supplier, so compare the calculator’s cubic-yard result with a local ready-mix quote rather than relying on a fixed size cutoff.

Multiple identical pours

For several identical footings, columns or post holes, enter the dimensions for one and set Quantity to the number of pours. The calculator multiplies the volume before adding any selected waste allowance.

How long until the concrete is ready?

Once it’s poured, curing takes time, and the right wait depends on the mix, weather and what the concrete will carry. See concrete curing time for a day-by-day guide covering 24 hours, 7 days and 28 days.

QUICK ANSWERS

Common concrete calculator questions

How many 80 lb bags of concrete are in a cubic yard?

Using a yield of about 0.60 cubic feet per 80 lb bag, one cubic yard requires about 45 bags because 27 ÷ 0.60 = 45. Check your specific product label because bag yield can differ by mix.

How many 60 lb bags are in a cubic yard?

At approximately 0.45 cubic feet per 60 lb bag, one cubic yard requires about 60 bags because 27 ÷ 0.45 = 60.

How thick should a concrete slab be?

A 4-inch slab is common for many residential patios and walkways, but the required thickness depends on soil conditions, reinforcement, loads, local code and the project design. Driveways and structural work may require a different thickness, so follow the plans or local requirements for the job.

How does the stair calculation work?

The stair option treats the stairs as a solid stepped prism. It uses stair width, tread depth, riser height and the number of steps. It does not include landings, voids, unusual nosings or other structural details, so use project drawings for a final structural quantity.

Does this calculator know concrete prices?

No. Bag and ready-mix prices vary by region, supplier and mix. Enter your own price per bag, cubic yard, cubic foot or cubic meter to estimate material cost.

What strength is QUIKRETE Concrete Mix No. 1101?

QUIKRETE’s current data sheet lists a typical 28-day compressive strength of 4,000 psi (27.5 MPa) for Concrete Mix No. 1101. Other products and project specifications can require a different mix or strength.