How Much Concrete Do I Need?
Calculate the exact amount of concrete for slabs, footings, walls, and columns. Get results in cubic yards and number of bags with cost estimates.
Enter your dimensions above to calculate concrete needed.
💡 1 cubic yard of concrete covers approximately 81 sq ft at 4 inches thick
How to Calculate Concrete Needed
Formula
Length (ft) × Width (ft) × Thickness (in) ÷ 324 = Cubic Yards
Multiply your slab's length by width to get square footage. Multiply by thickness in inches, then divide by 324 to convert to cubic yards.
Example
For a 10 ft × 12 ft patio slab at 4 inches thick: 10 × 12 × 4 ÷ 324 = 1.48 cubic yards. That's about 67 bags of 80-lb concrete mix.
Tips & Best Practices
- •Order 5–10% extra concrete to account for spillage, uneven ground, and forms.
- •Standard slab thickness is 4 inches. Driveways should be 5–6 inches.
- •One 80-lb bag of concrete mix yields about 0.6 cubic feet. You need 45 bags per cubic yard.
- •For projects over 1 cubic yard, consider ordering ready-mix delivery instead of mixing bags.
Quick Reference
1 cubic yard of concrete covers approximately 81 sq ft at 4 inches thick
Frequently Asked Questions
How much does a cubic yard of concrete cost?+
Ready-mix concrete costs $115–$165 per cubic yard delivered. Bagged concrete (mixing yourself) runs about $3–$5 per 80-lb bag, or roughly $135–$225 per cubic yard.
How many bags of concrete do I need?+
You need approximately 45 bags of 80-lb concrete mix per cubic yard, or about 60 bags of 60-lb mix per cubic yard.
How thick should a concrete slab be?+
Standard patios and walkways: 4 inches. Driveways: 5–6 inches. Garage floors: 6 inches. Always check local building codes for requirements.
How long does concrete take to cure?+
Concrete reaches about 70% strength in 7 days and full strength in 28 days. You can walk on it after 24–48 hours and drive on it after 7 days.