How Much Concrete for a 12×12 Slab?
Get exact concrete amounts, bag counts, and cost estimates for your 12×12 project.
Decision Guide
12x12 slab buying decision
A 12x12 slab is usually past the point where bags feel convenient. The real decision is whether thickness or load justifies a truck order now instead of a painful hand-mix weekend.
Ready-mix is the safer default
Plan around 1.96 yd³ with waste, or about 88 bags if you insist on hand mixing.
At this size, hauling and mixing effort usually becomes the hidden cost driver.
Before you order
- Waste-adjusted volume is the order number that matters.
- Thickness changes both budget and labor fast.
- Bag counts over a typical weekend mix threshold should trigger a method change.
Next steps
- Confirm whether the slab is patio-grade or load-bearing.
- Compare the waste-adjusted volume against a local truck quote.
- If the bag count sounds miserable, change methods now.
Common mistakes
- Treating a 12x12 slab like a small bag job.
- Using patio thickness for heavier slab loads.
- Comparing price without valuing labor and trips.
Use this as a planning guide. Real delivery minimums and site access can still change the cheapest method.
Quick Answer: Concrete for a 12×12 Slab
4" Thick (Patio/Walkway)
1.78 yd³
80 bags (80lb)
6" Thick (Driveway)
2.67 yd³
120 bags (80lb)
8" Thick (Heavy-duty)
3.56 yd³
160 bags (80lb)
Adjustable Calculator
Length and width are locked to 12×12. Adjust thickness and cost.
Results
12×12 Slab Cost Estimate
| Thickness | Yards | 80lb Bags | Concrete Cost | Total w/ Labor* |
|---|---|---|---|---|
| 4 inches | 1.78 | 80 | $249 | $700-$1,000 |
| 6 inches | 2.67 | 120 | $373 | $900-$1,200 |
| 8 inches | 3.56 | 160 | $498 | $1,100-$1,500 |
*Total includes forming, rebar, pouring, and finishing labor. Prices vary by region.
About a 12×12 Concrete Slab
A 12×12 slab (144 square feet) is one of the most common DIY concrete projects. It's the right size for a small patio, shed base, hot tub pad, or walkway section.
Common Uses for a 12×12 Slab
- Patio: Medium patio, larger shed base, BBQ pad
- Shed Foundation: Standard 12×12 shed base
- Hot Tub Pad: Requires 6"+ thickness for weight
- Walkway/Porch: Entryway landing
How to Calculate
Volume = 12 ft × 12 ft × (4 in ÷ 12) = 33.3 cu ft ÷ 27 = 1.78 cubic yards
Tips for Your 12×12 Slab
- Order 1.5 yards to account for waste (10% extra)
- Use 6" thickness for driveways or anything bearing weight
- Add wire mesh or fiber reinforcement for crack prevention
- For a shed, 4" is sufficient; for a hot tub, use 6-8"