Concrete Calculator
Calculate cubic yards, bags and total cost for any concrete pour — slabs, footings, columns and pads. Trusted by 50,000+ contractors monthly.
Dimensions
Concrete Required
How to Use the Concrete Calculator
This powerful tool helps you figure out exactly how much material your project requires. If you are wondering how much concrete do i need, simply enter the length, width, and depth in feet or meters. For rectangular slabs use the Slab/Pad tab, and for round columns use the Column/Tube tab. The calculator instantly returns the required volume with waste, cubic feet, cubic meters, bag count, and a cost estimate.
The Formula Behind the Calculator
For rectangular pours: Volume (ft³) = Length × Width × Depth
cubic yards of concrete = Volume ÷ 27
For round columns: Volume (ft³) = π × radius² × depth
Bags needed (80lb) = Volume ft³ ÷ 0.60
Add waste: Final volume = Volume × (1 + Waste% ÷ 100)
Bags vs. Ready-Mix — Which to Choose?
Under 0.5 yd³ — bags are more convenient and practical. You can mix this amount by hand or with a small rented mixer without worrying about delivery fees or minimum load charges.
0.5 to 1 yd³ — borderline. Worth calling your local supplier for a short-load price. Some suppliers have minimums that make delivery expensive, but mixing 40+ bags is labor-intensive.
Over 1 yd³ — ready-mix delivery is almost always cheaper per yard. It ensures a consistent mix and saves you hours of back-breaking labor.
Real-World Example
A 10 ft × 10 ft patio at 4 inches thick works out to 100 ft² × 0.333 ft = 33.3 ft³ ÷ 27 = 1.23 yd³. Adding 10% for waste brings that to 1.36 yd³. At $150 per yard, you're looking at around $204 for the concrete.
Frequently Asked Questions
How do I calculate concrete?
Multiply length × width × depth (all in feet) to get cubic feet. Divide by 27 to get cubic yards. Add 10% for waste. The concrete calculator above handles all of this automatically — just enter your dimensions.
How many bags of concrete do I need per cubic yard?
One cubic yard of concrete requires approximately 45 bags of concrete (80lb), 60 bags of 60lb, or 90 bags of 40lb.
What is the formula for concrete volume?
For rectangular pours: Volume (ft³) = Length × Width × Depth. Divide by 27 for cubic yards of concrete. For round columns: Volume = π × radius² × depth ÷ 27.
Should I add waste to my concrete order?
Yes — always add 5 to 10%. Ten percent is the standard recommendation to account for spillage, an uneven sub-base, and over-excavation. The calculator applies 10% by default, and you can adjust it.
How accurate is this concrete calculator?
The calculator uses the same industry-standard formulas used by ready-mix suppliers and construction estimating software. Results are typically within ±2% of professional estimates. Always verify with your local supplier before placing a large order.