Concrete Volume Calculator — Slabs, Columns, Cylinders & Footings
Calculate concrete volume for any shape — rectangular slabs, round columns, or circular slabs. Results in cubic yards, cubic feet, and bag count.
How to Use This Calculator
- Select the shape of your concrete pour from the dropdown
- Enter the dimensions for that shape
- Set the number of identical pieces if pouring multiple
- Adjust the waste factor (10% is standard)
- Click "Calculate" to see cubic yards, cubic feet, and bag count
How the Calculation Works
// Rectangular Slab / Footing:
volume_ft³ = length_ft × width_ft × (depth_in / 12)
// Round Column / Cylinder:
volume_ft³ = π × (diameter_in / 24)² × height_ft
// Circular Slab:
volume_ft³ = π × (diameter_ft / 2)² × (thickness_in / 12)
// To cubic yards (divide by 27), then add waste:
volume_yd³ = volume_ft³ / 27
total = volume_yd³ × (1 + waste_pct / 100) Volume depends on shape. Rectangular pours multiply L × W × depth. Cylinders/columns use π × r² × height. All results convert from cubic feet to cubic yards (÷ 27), then a waste factor is added to ensure you order enough material.
Variables:
- length_ft / width_ft: Horizontal dimensions of the pour in feet
- depth_in / thickness_in: Vertical depth of the pour in inches
- diameter_in: Diameter for round columns in inches
- waste_pct: Percentage of extra material to order (recommend 10%)
Pro Tips
- Always order 10% more concrete than calculated to account for spillage and over-excavation
- Round columns and piers use the cylinder formula: π × r² × height
- For stepped footings, calculate each section separately then add totals
- Bag concrete is most cost-effective under 1 cubic yard — use ready-mix for larger pours
Recommended Products
QUIKRETE 80 lb Concrete Mix
Standard 4000 PSI ready-mix for slabs, footings, and steps.
View on Amazon →QUIKRETE 50 lb Fast-Setting Concrete
Sets in 20-40 minutes — ideal for posts and small pours.
View on Amazon →Marshalltown 16" x 3-3/4" Magnesium Bull Float
Smooth and level fresh concrete surfaces.
View on Amazon →Bon Tool 48" Concrete Finishing Trowel
Professional steel trowel for smooth concrete finishing.
View on Amazon →Frequently Asked Questions
How many cubic yards do I need for a 10×10×4" slab?
A 10×10 ft slab at 4 inches thick is 1.23 cubic yards (net). Add 10% waste → order about 1.35 cubic yards.
How do I calculate concrete for a round column?
Use the cylinder formula: π × (radius in ft)² × height in ft. A 12" diameter, 4 ft tall column = π × 0.25 × 4 ≈ 3.14 ft³ = 0.12 yd³.
How many 80 lb bags of concrete per cubic yard?
One 80 lb bag yields about 0.60 ft³. Since 1 cubic yard = 27 ft³, you need approximately 45 bags per cubic yard.
Should I use ready-mix or bagged concrete?
Use bagged concrete for projects under 1 cubic yard. For larger pours, ready-mix delivery is more economical and easier to manage.
What is a standard concrete mix ratio?
A standard 4000 psi residential slab uses a 1:2:3 ratio (1 part cement, 2 parts sand, 3 parts gravel), or simply use pre-mixed bags.