Planning result
A 10x12 slab at 4 inches thick uses about 1.48 cubic yards before waste and about 1.63 cubic yards with 10% waste. If using 80 lb bags with 0.6 cubic ft yield, plan roughly 74 bags after waste.
Assumptions
| Slab size | 10 ft by 12 ft. |
|---|---|
| Thickness | 4 inches, converted to 0.333 ft. |
| Waste | 10% for grade variation and forms. |
| Bag yield | 0.6 cubic ft per 80 lb bag for planning. |
Calculation
| Step | Result | Formula |
|---|---|---|
| Area | 120 sq ft | 10 x 12 |
| Volume | 40.0 cubic ft | 120 x 0.333 |
| Cubic yards | 1.48 yd3 | 40 / 27 |
| With waste | 1.63 yd3 | 1.48 x 1.10 |
| 80 lb bags before waste | 67 bags | 40 / 0.6, rounded up |
| 80 lb bags with waste | 74 bags | 67 x 1.10, rounded up |
Ready-mix is usually easier
This bag count is high for hand mixing. Ready-mix delivery may be more practical if access, minimum order, and timing work for the project.
Add thickened edges separately
This example assumes a flat 4 inch slab. Thickened edges, footings, piers, and low spots need additional volume.
Next step
Use the linked calculator or planning hub to adjust dimensions, waste, coverage, depth, spacing, or product packaging for the real project.
Related guides
FAQ
How many yards for a 10x12 four-inch slab?
About 1.48 cubic yards before waste and about 1.63 cubic yards with 10% waste.
Can I pour a 10x12 slab with bags?
It is possible, but the bag count is high and mixing time matters.
Does this include gravel base?
No. Base gravel is a separate estimate.