Concrete for a 12×12 ft slab
A 12 × 12 ft slab at 4 in deep needs 1.78 cubic yards of concrete — about 80 × 80 lb bags, roughly 3.60 tons and $293.33 of material. Fine-tune below.
Full breakdown
| Item | Value |
|---|---|
| Volume before waste | 48.0 ft³ |
| Volume with 5% waste | 50.4 ft³ |
| Cubic yards | 1.87 |
| Cubic metres | 1.43 |
| Cubic feet | 50.4 |
| Weight | 3.78 tons (7,560 lb) |
| Full dump-truck loads | 1 × 10 yd³ truck |
| 80 lb bags | 85 bags · $582.25 |
| 60 lb bags | 113 bags · $615.85 |
| Sq ft covered at 1 in deep | 605 |
| Sq ft covered at 3 in deep | 202 |
- Formula: length × width × depth, with depth converted from inches to feet (÷ 12), then × (1 + waste%).
- Concrete: Concrete is ordered by the cubic yard from a ready-mix plant, or mixed from 60 lb and 80 lb bags for small pours.
- Ready-mix plants almost always have a minimum charge — often 1 cubic yard — plus a short-load fee below about 3 yards, so a 0.5-yard pour can cost nearly as much as a 3-yard one.
- Prices are national averages for planning, not quotes. Confirm with a local supplier — delivery, short-load fees and tax are extra.
12 × 12 ft is 144 square feet. Spread 4 in deep, that is 48.0 cubic feet, or 1.78 cubic yards, of concrete. Expect to order around 3.60 tons.
The calculator above is pre-filled with these dimensions — change any field to see the numbers update. Concrete is ordered by the cubic yard from a ready-mix plant, or mixed from 60 lb and 80 lb bags for small pours.
Frequently asked questions
How many cubic yards of concrete for a 12×12 ft slab?
About 1.78 cubic yards at 4 in deep, which is 48.0 cubic feet or 3.60 tons. Add 5% waste if the ground is uneven.
How many bags is that?
80 × 80 lb bags, or 107 × 60 lb bags. Bagged is only worth it at this size if you cannot take a truck delivery.
What depth should a slab be?
4 in is the standard for concrete in this application. Ready-mix plants almost always have a minimum charge — often 1 cubic yard — plus a short-load fee below about 3 yards, so a 0.5-yard pour can cost nearly as much as a 3-yard one.