DIY Concrete Mix Calculator
Calculate how many bags of cement, sand, and gravel you need for your concrete project.
Covers slabs, footings, and posts.
Materials Needed
Concrete volume is calculated from the dimensions of your project:
Volume = Length × Width × Depth
When using feet: result is in cubic feet, then converted to cubic yards (÷ 27).
When using meters: result is in cubic meters.
When using inches: each dimension is converted to feet first (÷ 12).
A standard concrete mix ratio is 1:2:3 (cement : sand : gravel) by volume.
Pre-mixed bag coverage:
- 40 lb bag: 0.011 cubic yards (0.30 cu ft)
- 60 lb bag: 0.017 cubic yards (0.45 cu ft)
- 80 lb bag: 0.022 cubic yards (0.60 cu ft)
Add 10% extra for waste and spillage. For post holes, calculate the cylinder volume:
Volume = π × radius² × depth
1 cubic yard = 27 cubic feet = 0.7646 cubic meters