How to Calculate Concrete for Columns
Whether you're pouring round Sonotube columns for a deck or square structural columns for a commercial building, getting the concrete quantity right prevents waste and costly short-load fees.
Round Column Formula
Volume = π × (diameter/2)² × height
Convert to cubic yards by dividing by 27 (since there are 27 cubic feet in a cubic yard). Make sure all measurements are in feet before calculating.
Square Column Formula
Volume = side × side × height
Again, all measurements should be in feet, and divide by 27 to get cubic yards.
Bags vs. Ready-Mix for Columns
For small jobs (1-3 columns under 12" diameter), bagged concrete is often more practical. For larger columns or more than 4-5 columns, ready-mix delivery is more cost-effective. The break-even point is typically around 1 cubic yard — below that, bags are cheaper; above, ready-mix wins.
- 80 lb bag yields ~0.022 cubic yards (0.6 cu ft)
- 60 lb bag yields ~0.017 cubic yards (0.45 cu ft)
- 1 cubic yard = approximately 45 bags (80 lb) or 60 bags (60 lb)
Sonotube Tips
- Brace tubes plumb with 2×4 supports on at least 2 sides
- Set anchor bolts or post brackets while concrete is still wet
- Pour in lifts (2 ft at a time) and vibrate to eliminate voids
- Leave tubes in place for 24-48 hours before stripping
- For below-grade sections, coat the outside with waterproofing
Need a Professional Estimate?
Use our Pro Estimate Template to turn these calculations into a professional bid sheet with material breakdown, labor costs, and profit margins.