Primary material
62 bags
80 lb concrete mix
Use the calculated bag count as your buying starting point, then verify yield and pallet limits with the store.
12 x 12 concrete slab
How much concrete for a 12x12 slab?
A 12 ft by 12 ft slab is 144 square feet. At 4 inches thick it needs about 1.96 cubic yards or 88 bags of 80 lb mix with 10% waste. Adjust thickness, waste, and price below, or see the 4/5/6 inch breakdown.
12 x 12 x 4 in
1.96 yd³
88 bags at 80 lb
Area
144 sq ft
12 ft x 12 ft
Material cost (4 in)
$293
ready-mix, material only
12x12 by thickness
Concrete for a 12x12 slab at 4, 5, and 6 inches
Thickness drives the volume. Patios and shed pads often use 4 inches; driveways and heavier loads step up to 5 or 6 inches. All figures include the default 10% waste.
| Thickness | Cubic yards | 80 lb bags | 60 lb bags | Ready-mix material |
|---|---|---|---|---|
| 4 in | 1.96 yd³ | 88 | 118 | $293 |
| 5 in | 2.44 yd³ | 110 | 147 | $367 |
| 6 in | 2.93 yd³ | 132 | 176 | $440 |
Want installed cost?
The figures here are material only. For labor, base prep, forms, and finishing, the concrete cost calculator gives a full installed range.
Shopping list
Ready to price and order
Use the calculated quantities as a starting cart, then compare store availability, delivery fees, pallet limits, and local ready-mix minimums before buying.
Large pours
Ready-mix quote check
For high bag counts, compare the bagged route against local ready-mix minimums, delivery, access, and unload time.
Optional base
Gravel base
Base depth is project-specific. Estimate it separately before adding bags or bulk gravel to the order.
Optional forms
Forms and stakes
Plan lumber, stakes, screws, release, and bracing around the perimeter and any step-downs or curves.
Store buttons open retailer search results for now. Confirm exact product yield, pickup, delivery, and pallet rules before ordering.
Formula shown
How the 12x12 estimate works
1. Area is fixed at 144 sq ft
12 ft x 12 ft = 144 sq ft
2. Volume in cubic feet
144 sq ft x (thickness in / 12)
3. Yards, waste, and bags
yd³ = ft³ / 27; bags = ceil(ft³ x (1 + waste) / bag yield)
Watch the edges
A thickened edge, a low subgrade spot, or over-excavation adds concrete fast. Bump the waste percentage up if the base is rough, and estimate any beam or haunch separately.
Sources
- Quikrete product yields — bagged concrete mix yield references
- Sakrete bagged concrete references — common bag sizes and concrete mix guidance
- ConcreteNetwork concrete price guide — ready-mix and installed concrete cost context
Reviewed for estimating accuracy
Last updated: June 25, 2026
Estimate only.
This calculator is not a quote. Verify product yield, price, delivery minimums, and local conditions with your supplier or contractor before buying materials.
FAQ
12x12 concrete slab questions
Bags, cubic yards, thickness, cost, and bags-vs-ready-mix for a 12 ft by 12 ft slab.
How much concrete do I need for a 12x12 slab? + -
A 12 ft by 12 ft slab at 4 inches thick needs about 1.96 cubic yards with the default 10% waste. That is roughly 88 bags of 80 lb mix or 118 bags of 60 lb mix. At 5 inches it rises to 2.44 yd³ and at 6 inches to 2.93 yd³.
How many 80 lb bags of concrete for a 12x12 slab? + -
About 88 bags of 80 lb concrete mix for a 4 inch slab with 10% waste, 110 bags at 5 inches, and 132 bags at 6 inches. At that bag count most people order ready-mix instead.
How many yards of concrete for a 12x12 slab? + -
A 12x12 slab is 144 square feet. At 4 inches that is about 1.96 cubic yards including 10% waste — typically a 2 to 2.5 yard ready-mix order once you round up. Check the supplier minimum load.
How much does a 12x12 concrete slab cost? + -
Material alone for a 4 inch 12x12 slab is roughly $293 by ready-mix or $506 in 80 lb bags at typical prices. Installed cost adds labor, base prep, forms, and finishing and varies by region — use the concrete cost calculator for a full installed range.
Should I use bags or ready-mix for a 12x12 slab? + -
A 4 inch 12x12 slab needs around 88 bags, which is heavy mixing for one day. A slab this size is usually easier and more consistent with ready-mix, but compare the bag total against the ready-mix minimum and delivery fee.