Whether you're pouring a backyard patio, a foundation footing, fence post piers, or a stair set, knowing exactly how much concrete to order saves money and prevents mid-pour runs to the store. This calculator handles five common shapes and gives you results in cubic yards, cubic meters, and bag count — everything you need before you call the ready-mix plant or load the truck.

Step 1: Select Your Shape

Choose the shape that matches your project.

  • Slab — driveways, patios, basement floors, and garage slabs. Defined by length, width, and thickness.
  • Footing — continuous strip footings beneath walls or foundations. Same formula as a slab, oriented vertically with a "depth" dimension.
  • Column — square or rectangular piers and posts. All three dimensions use the same primary unit.
  • Round Col. — cylindrical sonotube piers common for decks and fences. Enter the tube diameter and height.
  • Stairs — concrete stair sets. Enter the number of steps, stair width, and the rise and run per step.

Step 2: Choose Your Units

Toggle between ft / in and m / cm. Major dimensions (length, width, height) use the primary unit. Cross-section measurements (thickness, depth, diameter, rise, run) use the smaller sub-unit for precision. The calculator converts everything internally — just enter the numbers you have.

Step 3: Enter Dimensions

Measure carefully. Common defaults to know:

  • Residential slab thickness: 4 in (foot traffic) or 6 in (vehicles)
  • Footing depth: 12 in minimum, deeper in freeze-thaw climates
  • Deck pier (sonotube): 12 in or 16 in diameter
  • Standard stair rise: 7 in; standard run: 11 in
  • Fence post footing: diameter = 3× post width, depth = 1/3 post height

Step 4: Set Options

Select your bag size — 60 lb bags yield 0.45 cu ft each; 80 lb bags yield 0.60 cu ft. For projects under half a cubic yard, bagged concrete is cost-effective. Above one cubic yard, a ready-mix order is almost always cheaper and faster.

Set the price per cubic yard to match your local ready-mix supplier. Prices vary widely by region — $100–$175/yd³ is typical in the U.S. as of 2026.

Reading the Results

  • Cubic yards — the standard U.S. ordering unit. A standard mixer truck carries 8–10 yd³.
  • Cubic meters — for metric projects and international reference.
  • Bag count — number of pre-mixed bags needed, rounded up.
  • Estimated cost — volume × your entered price per cubic yard.

Pro Tips for Accurate Estimates

Always order 10% extra. Uneven sub-grades, spillage, and slight under-fills add up quickly. The results panel reminds you of this.

Don't add extra water on site. Adding water beyond the specified water-to-cement ratio weakens the mix. A 4,000 PSI mix at 0.45 w/c is standard for most structural slabs.

Cure properly. Concrete reaches ~70% of design strength in 7 days and full strength at 28 days. Keep it moist and above 50°F (10°C) for the first week. Plastic sheeting or a curing compound both work.

Control joints prevent cracking. For slabs, cut control joints every 8–12 feet in both directions, to a depth of 1/4 the slab thickness. This guides where the slab cracks so the cracks are straight and hidden.

Formulas Used

  • Slab / Footing: L × W × T ÷ 27 (yd³)
  • Column: L × W × H ÷ 27
  • Round column: π × (D÷2)² × H ÷ 27
  • Stairs: Steps × Width × Rise × Run ÷ 27

Bag coverage per Quikrete/Sakrete spec: 60 lb = 0.45 cu ft; 80 lb = 0.60 cu ft. 1 yd³ = 27 ft³ = 0.765 m³.