Concrete Calculator

Concrete is evaluated from Shape, Length and Width. The calculation reports Cubic Feet, Cubic Yards and 60 lb Bags Needed.

Results

Thanks — we’ve logged this for review.

About the Concrete Calculator

Concrete is treated here as a quantitative relation between Shape, Length, Width and Thickness/Depth and Cubic Feet, Cubic Yards, 60 lb Bags Needed and 80 lb Bags Needed.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Slab/Pad: Volume = length (ft) x width (ft) x thickness (in) / 12
Footing/Trench: Same formula (width = footing width)
Column/Cylinder: Volume = pi x (diameter/2)^2 x height (all in feet)
60-lb bags per yd^3: 1 yd^3 / 0.0222 yd^3/bag = ~45 bags
80-lb bags per yd^3: 1 yd^3 / 0.0296 yd^3/bag = ~34 bags
Add 10% waste factor for over-ordering (standard practice).

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Slab/Pad: Volume = length (ft) x width (ft) x thickness (in) / 12
Footing/Trench: Same formula (width = footing width)
Column/Cylinder: Volume = pi x (diameter/2)^2 x height (all in feet)
60-lb bags per yd^3: 1 yd^3 / 0.0222 yd^3/bag = ~45 bags
80-lb bags per yd^3: 1 yd^3 / 0.0296 yd^3/bag = ~34 bags
Add 10% waste factor for over-ordering (standard practice).

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: Backyard patio: 12 ft × 10 ft × 4 in

Inputs

shape: Slab/Pad length: 12 width: 10 depth: 4
Cubic Feet: 40 ft^3. Cubic Yards: 1.48 yd^3. 60 lb Bags Needed: 67 bags. 80 lb Bags Needed: 51 bags. Cubic Yards + 10% Waste: 1.63 yd^3

With Shape = Slab/Pad, Length = 12, Width = 10 and Thickness/Depth = 4 as the stated inputs, the result is Cubic Feet = 40 ft^3, Cubic Yards = 1.48 yd^3 and 60 lb Bags Needed = 67 bags. Each value corresponds to the declared output fields.

Example 2: Driveway: 20 ft × 18 ft × 6 in

Inputs

shape: Slab/Pad length: 20 width: 18 depth: 6
Cubic Feet: 180 ft^3. Cubic Yards: 6.67 yd^3. 60 lb Bags Needed: 300 bags. 80 lb Bags Needed: 227 bags. Cubic Yards + 10% Waste: 7.33 yd^3

With Shape = Slab/Pad, Length = 20, Width = 18 and Thickness/Depth = 6 as the stated inputs, the result is Cubic Feet = 180 ft^3, Cubic Yards = 6.67 yd^3 and 60 lb Bags Needed = 300 bags. Each value corresponds to the declared output fields.

Example 3: Deck footings: 4 columns, 10-in diameter × 48 in deep

Inputs

shape: Column/Cylinder length: 4 depth: 48 diameter: 10
Cubic Feet: 8.73 ft^3. Cubic Yards: 0.32 yd^3. 60 lb Bags Needed: 15 bags. 80 lb Bags Needed: 11 bags. Cubic Yards + 10% Waste: 0.36 yd^3

With Shape = Column/Cylinder, Length = 4, Thickness/Depth = 48 and Diameter = 10 as the stated inputs, the result is Cubic Feet = 8.73 ft^3, Cubic Yards = 0.32 yd^3 and 60 lb Bags Needed = 15 bags. Each value corresponds to the declared output fields.

Example 4: Sidewalk section: 4 ft × 40 ft × 4 in

Inputs

shape: Slab/Pad length: 40 width: 4 depth: 4
Cubic Feet: 53.33 ft^3. Cubic Yards: 1.98 yd^3. 60 lb Bags Needed: 89 bags. 80 lb Bags Needed: 68 bags. Cubic Yards + 10% Waste: 2.17 yd^3

With Shape = Slab/Pad, Length = 40, Width = 4 and Thickness/Depth = 4 as the stated inputs, the result is Cubic Feet = 53.33 ft^3, Cubic Yards = 1.98 yd^3 and 60 lb Bags Needed = 89 bags. Each value corresponds to the declared output fields.

Common Use Cases

  • Calculate concrete for a driveway or patio slab
  • Estimate concrete needed for fence post footings
  • Determine ready-mix concrete bags for a small pour