Concrete Formula
Cubic Feet = Length × Width × (Thickness ÷ 12) Cubic Yards = Cubic Feet ÷ 27 60-lb Bags = Cubic Feet ÷ 0.45 80-lb Bags = Cubic Feet ÷ 0.60
Recommended Slab Thickness
| Project | Thickness | Notes |
|---|---|---|
| Walkway / patio | 3–4 inches | Light foot traffic |
| Residential driveway | 4 inches | Standard passenger vehicles |
| Garage slab | 4–6 inches | Heavier vehicles |
| Footing | 8–12 inches | Depends on load and soil |
| Commercial slab | 6+ inches | Forklifts and heavy loads |
Bags vs. Ready-Mix
Use our free calculator above to compare bag count vs. ready-mix cost before you order. Mixing bags is cost-effective for small projects under 1 cubic yard. For anything larger, ready-mix concrete delivered by truck is faster, more consistent, and often cheaper per yard. Most ready-mix suppliers have a minimum order of 1 yard.
Frequently Asked Questions
How many 80-lb bags of concrete make a yard?+
It takes approximately 45 bags of 80-lb concrete to make one cubic yard. For 60-lb bags, you need about 60 bags per cubic yard.
How thick should a concrete driveway slab be?+
A residential driveway should be at least 4 inches thick for standard vehicles. For heavier trucks or loads, use 5–6 inches. Always place concrete over a 4-inch compacted gravel base.
How much does a yard of ready-mix concrete cost?+
Ready-mix concrete typically costs $125–$200 per cubic yard depending on region, mix design, and supplier. Most companies have a minimum order of 1 yard and charge a short-load fee for orders under 3–5 yards.
When should I use bags instead of ready-mix?+
Bagged concrete is practical for projects under 0.5–1 cubic yard — small footings, fence posts, or repairs. For anything larger, ready-mix is faster, stronger, and often cheaper when labor is considered.