To figure out concrete yardage (how much concrete you need), use this formula:
- Measure the length, width, and depth (thickness) of the area to be concreted in feet.
- Multiply length × width × depth to get the volume in cubic feet.
- Divide the result by 27 (since there are 27 cubic feet in 1 cubic yard) to convert cubic feet to cubic yards.
If your depth is in inches, convert it to feet first by dividing by 12. Example: For a 25 ft long, 5 ft wide sidewalk, 4 inches deep:
- Convert 4 inches to feet: 4 ÷ 12 = 0.333 ft
- Calculate volume in cubic feet: 25 × 5 × 0.333 = 41.625 cubic feet
- Convert to cubic yards: 41.625 ÷ 27 = 1.54 cubic yards
This is the amount of concrete needed. It's recommended to order a little extra (about 10%) to account for spillage or uneven thickness. Summary formula:
Concrete (cubic yards)=Length (ft)×Width (ft)×Depth (ft)27\text{Concrete (cubic yards)}=\frac{\text{Length (ft)}\times \text{Width (ft)}\times \text{Depth (ft)}}{27}Concrete (cubic yards)=27Length (ft)×Width (ft)×Depth (ft)
If depth is in inches, convert by:
Depth (ft)=Depth (inches)12\text{Depth (ft)}=\frac{\text{Depth (inches)}}{12}Depth (ft)=12Depth (inches)
This method works for rectangular slabs, driveways, sidewalks, and similar projects.
