Concrete Calculator
Estimate concrete for slabs, footings or columns in cubic yards.
Concrete needed
0.81 cu yd
- Total volume
- 20 ft³
- Pre-mixed 60lb bags
- 49 bags
- Pre-mixed 80lb bags
- 37 bags
Estimated material cost
$134
How we calculate this
For slabs and footings: volume = length × width × thickness ÷ 27. For columns and round footings: volume = π × radius² × height, using diameter ÷ 2 for the radius. Multiply by quantity for repeated footings (e.g. multiple fence post holes).
Example
Measuring tips
For footings, measure the hole diameter and depth. For slabs, use the Concrete Slab Calculator for a more focused workflow with bag-count output.
Common mistakes
- Forgetting to multiply by quantity when pouring multiple identical footings.
- Mixing up diameter and radius when entering column dimensions.
- Not adding waste for spillage, especially on small footing pours.
Frequently asked questions
How much concrete do I need for fence post footings?
Select "Column / round footing," enter your hole diameter and depth, and the number of posts — the calculator multiplies for you.
What is the difference between this and the Concrete Slab Calculator?
This calculator also supports footings and columns; the Concrete Slab Calculator is a slab-only, bag-count-focused version of the same math.
Related calculators
Estimates are provided for planning purposes. Actual material requirements may vary based on supplier specifications, compaction, site conditions, installation method, waste, and local code.