🧱 Concrete Volume Calculator

Estimate how much concrete you need for slabs, footings, rectangular columns, and tubes (sonotubes). Enter your dimensions to see total volume in cubic feet and cubic yards, plus 40, 60, and 80 lb bag counts so you can plan orders and avoid short loads.

Concrete volume results

Enter dimensions for at least one shape, then choose Calculate Concrete Volume to see your total in cubic feet, cubic yards, and approximate bag counts.

Concrete volume breakdown by shape

Once you calculate a result, this section shows the volume contribution from each shape so you can see where most of your concrete is going.

Concrete volume calculator inputs and key terms

This calculator uses common shapes found in residential and light commercial projects. Here's what each input means and how it's used.

• Slab length and width (feet): The dimensions of a rectangular slab such as a patio, driveway, or equipment pad. Measured in feet.
• Slab thickness (inches): The thickness of the slab, typically 4" for light-duty patios and 4–6" or more for driveways and garages.
• Footing length (feet): The linear length of a strip or wall footing.
• Footing width and thickness (inches): The cross-section dimensions of the footing. Wider footings spread load over a larger soil area.
• Rectangular column width and depth (inches): The cross section of a rectangular pier or column.
• Column height (feet): The vertical height of the column or pier above the footing or grade.
• Tube diameter (inches): The inside diameter of a round form such as a sonotube used for deck posts or porch columns.
• Tube height (feet): The vertical height of the pour inside the tube.
• Number of shapes: For each shape type, the calculator multiplies the volume of one shape by the quantity you enter.
• Cubic feet (ft³): A standard volume unit. Concrete bag yields and many small projects are often estimated in cubic feet.
• Cubic yards (yd³): The standard unit for ready-mix truck orders. One cubic yard equals 27 cubic feet.
• 40, 60, and 80 lb bag counts: Approximate numbers of pre-bagged concrete required based on typical yield per bag size. Real products can vary slightly, so always check the bag label.

Formulas used in the Concrete Volume Calculator

These are standard volume formulas used in concrete estimating and construction. All dimensions are converted to feet and feet-based units before calculating volume.

1. Slab volume (rectangular)

Let:
L = slab length in feet
W = slab width in feet
T = slab thickness in inches
N = number of identical slabs
Convert thickness to feet: Tft = T ÷ 12
Slab volume (ft³) = L × W × Tft × N

2. Footing volume (rectangular beam)

Let:
L = footing length in feet
W = footing width in inches
T = footing thickness in inches
N = number of identical footings
Convert to feet: Wft = W ÷ 12, Tft = T ÷ 12
Footing volume (ft³) = L × Wft × Tft × N

3. Rectangular column volume

Let:
W = column width in inches
D = column depth in inches
H = column height in feet
N = number of columns
Convert to feet: Wft = W ÷ 12, Dft = D ÷ 12
Column volume (ft³) = Wft × Dft × H × N

4. Tube (cylindrical) volume

Let:
D = tube diameter in inches
H = tube height in feet
N = number of tubes
Convert to feet and radius: Rft = (D ÷ 12) ÷ 2
Tube volume (ft³) = π × Rft² × H × N

5. Total volume and bag counts

Total ft³ = Slab volume + Footing volume + Column volume + Tube volume
Total yd³ = Total ft³ ÷ 27
Approximate bag counts (rounded up):
40 lb bags ≈ Total ft³ ÷ 0.30
60 lb bags ≈ Total ft³ ÷ 0.45
80 lb bags ≈ Total ft³ ÷ 0.60

These yields are typical for ready-to-use bagged concrete, but always confirm the yield listed on the product packaging for your specific mix.

Concrete Volume Calculator FAQs

• How accurate are the concrete volume and bag estimates?
  The volume formulas are mathematically precise for the shapes you enter, assuming the measurements and units are correct. Bag counts are based on typical yields for 40, 60, and 80 lb bags and are rounded up. In the field, you should usually add 5–10% extra for waste, uneven subgrades, and minor plan changes.
• Should I order concrete by the bag or by the cubic yard?
  Small projects like single posts, small pads, and short walkways are often easier with bagged concrete from a home center. Larger projects such as driveways, garage slabs, and long footings are usually more economical and consistent when ordered by the cubic yard from a ready-mix supplier. This calculator shows both so you can compare.
• Why do I enter some dimensions in feet and others in inches?
  In construction, slab and footing lengths are commonly measured in feet, while thicknesses and widths are often specified in inches. The calculator converts everything to feet internally before computing volume, which matches how estimators and suppliers typically work.
• Do I need to include a waste factor in the calculator?
  The calculator gives you the theoretical volume for the shapes you enter. Most contractors then add a waste factor—often 5–10%—to cover spillage, over-excavation, and uneven forms. You can apply that percentage to the total cubic yards or bag counts shown here when you place your order.
• Can I use this calculator for metric units?
  This version is designed for feet, inches, and U.S. customary units. If you work in metric, you can convert dimensions to feet and inches first, or use a metric-specific calculator. In the future, we may add a dedicated metric concrete calculator for m³ and millimeters.
• Does the calculator account for reinforcement or base material?
  No. The calculator only estimates concrete volume based on shape geometry. It does not add material for gravel base, rebar, wire mesh, or fibers. Those items are specified separately in your project plan or building code requirements and should be estimated in addition to concrete volume.