Estimate Cubic Yards, Bags of Concrete & Total Cost — Free for Contractors & DIYers
Whether you are pouring a backyard patio, a garage floor, or a set of deck footings, getting your concrete math right before you order saves time and money. Ordering too little means a second delivery charge. Ordering too much means wasted material. Here is everything you need to know.
Measure length and width in feet. Measure depth or thickness in inches and convert to feet by dividing by 12. For slabs, depth is the slab thickness. For footings, depth is how deep the footing sits. For walls, depth is the wall thickness.
Multiply length x width x depth (all in feet). This gives you cubic feet. Example: a 12 x 20 slab at 4 inches thick is 12 x 20 x 0.333 = 80 cubic feet.
Divide cubic feet by 27 (since 1 cubic yard = 27 cubic feet). From the example above: 80 divided by 27 = 2.96 cubic yards.
Always add at least 10% for waste, uneven subgrade, and spillage. Multiply your cubic yards by 1.10. For the example: 2.96 x 1.10 = 3.26 cubic yards to order.
For projects under 0.5 cubic yards, bagged concrete is often cheaper and more practical. For anything larger, ready-mix delivered by truck is more economical and much less labor-intensive.
| Slab Size | Thickness | Cubic Yards | 80 lb Bags | Est. Cost (Ready-Mix) |
|---|---|---|---|---|
| 10 x 10 ft | 4 in | 1.23 yd3 | 56 bags | $160-$235 |
| 10 x 10 ft | 6 in | 1.85 yd3 | 84 bags | $240-$355 |
| 12 x 12 ft | 4 in | 1.78 yd3 | 81 bags | $230-$340 |
| 12 x 20 ft | 4 in | 2.96 yd3 | 135 bags | $385-$565 |
| 20 x 20 ft | 4 in | 4.94 yd3 | 225 bags | $640-$940 |
| 20 x 20 ft | 6 in | 7.41 yd3 | 337 bags | $965-$1,410 |
| 24 x 24 ft | 4 in | 7.11 yd3 | 323 bags | $925-$1,350 |
| 30 x 30 ft | 5 in | 13.89 yd3 | 631 bags | $1,806-$2,640 |
One cubic yard of concrete covers different areas depending on thickness:
Ready-mix concrete prices vary significantly by region. In 2026, typical ranges are:
PSI stands for pounds per square inch — it measures concrete compressive strength after curing. Here is a quick guide for choosing the right mix:
For most DIY and residential contractor projects, a 3000-3500 PSI mix with a 4-5 inch slump is the correct choice. Always consult your local building department for code requirements on permitted work.
Rebar and wire mesh both add tensile strength that concrete lacks on its own. Here is when to use each:
Rebar is typically placed in a 12-18 inch grid pattern and tied at intersections. Cost runs $0.50-$1.50 per square foot depending on bar size and spacing.
Measure your project dimensions in feet (length x width x depth). Depth must be converted from inches to feet by dividing by 12. Multiply all three values to get cubic feet, then divide by 27 to get cubic yards. Add 10% for waste. Our calculator above does this automatically for slabs, footings, walls, and round columns.
A 10x10 slab at 4 inches thick requires 1.23 cubic yards — about 56 bags of 80 lb concrete (each bag yields roughly 0.60 cubic feet). Add 10% waste and you will need approximately 62 bags. For 6 inches thick, plan on 84 bags before waste.
A standard ready-mix truck holds 8-10 cubic yards. Some large trucks carry up to 12 yards. For projects under 1 cubic yard, use bagged concrete. For 1-4 yards, expect a short-load fee of $75-$200 since trucks cannot fill to capacity.
National average in 2026 is $130-$190 per cubic yard for standard 3000 PSI ready-mix. Southeast and Midwest tend to run lower ($120-$150), while West Coast and Northeast run higher ($155-$200+). High-strength mixes and fiber-reinforced concrete cost 10-20% more.
Standard residential patios and walkways: 4 inches. Driveways: 5-6 inches. Garage floors with vehicle traffic: 5-6 inches. Commercial or heavy-equipment slabs: 6-8 inches. Always check your local building code for minimum thickness requirements on permitted work.
Waste factor accounts for uneven subgrade, spillage, forms that are not perfectly level, and rounding errors. Add 10% for standard projects. For irregular shapes, steps, or rough terrain, add 15%. Never order the exact calculated amount — you will almost always run short.