Understanding Concrete Volume
Concrete is universally ordered in **cubic yards ($\text{yd}^3$)**. A cubic yard is a volume of 27 cubic feet (a cube 3 feet on all sides). Accurate measurement and adding a contingency factor are vital for a successful pour.
Calculation Logic
The calculation converts all measurements to feet, computes the volume, and then converts the result to cubic yards. $$\text{Depth in Feet} = \frac{\text{Depth (in)}}{\text{12}}$$ $$\text{Volume (ft}^3) = \text{Length (ft)} \times \text{Width (ft)} \times \text{Depth (ft)}$$ $$\text{Volume (yd}^3) = \frac{\text{Volume (ft}^3)}{\text{27}}$$ Note: Concrete suppliers typically have a minimum order (e.g., 1 cubic yard). Always round your order up to the nearest $\frac{1}{4}$ or $\frac{1}{2}$ yard.
Standard Depths
4 Inches ($\mathbf{4"}$ Depth)
- Best for pedestrian areas: patios, sidewalks, walkways.
- Requires proper sub-base preparation (gravel).
- Least expensive option per square foot.
6 Inches ($\mathbf{6"}$ Depth)
- Required for vehicle traffic: driveways, garage floors.
- Provides the necessary strength for heavier loads.
- Recommended for areas with heavy equipment or poor soil.
Critical Tip:
Always order extra concrete! It's much cheaper to send a little back than to be short on the day of the pour. The recommended 5% contingency helps cover sloped forms and unlevel ground.