12x12 Concrete Slab, 4 Inches Thick
A 12 × 12 ft slab (144 sq ft) at 4 in thick takes about 1.96 cubic yards of concrete, with 10% extra for waste. For ready-mix, order 2 cu yd for the 12x12, about $340 – $470 delivered, short-load fee included. Bagged, the same 12x12 is 88 80 lb or 118 60 lb bags, about $590 – $826 for the concrete alone.
- Ready-mix order
- 2 cu yd
- Ready-mix cost
- $340 – $470
- 80 lb bags
- 88
- Bag cost
- $590 – $826
Materials only for a 12x12 at 4 in, from national price ranges as of 2026-09; not a live quote.
Hot tub, shed or patio: the 12x12 slab
A 12x12 square is the size most often poured for a hot tub, because it leaves about 2 ft of walking room around a 7 to 8 ft tub and space for the steps and the cover lifter.
A filled hot tub with people in it commonly weighs somewhere between 3,000 and 6,000 lb, so read the maker's pad spec: many accept a level 4 in slab, while some ask for more thickness or reinforcement.
The same footprint also suits a 12x12 shed or a square patio with a small dining set, where it has a little more room than a 10x10.
A 4 in 12x12 pour: check first
- For a hot tub, plan the electrical before the pour: the NEC wants a disconnect within sight of the tub and at least 5 ft from it.
- A hot-tub pad should be flat and level, not sloped like a patio; use a small drain path at the edge instead.
- At 144 sq ft, a shed on this pad may be over your town's permit-free limit, so ask first.
Full plan for a 12x12 slab, 4 in
- Area
- 144 sq ft
- Thickness
- 4 in
- Volume
- 1.96 cu yd
Bagged concrete estimate (DIY)
$730 – $1,053
Est. as of 2026-09 — not a live quote
Ready-mix delivered, incl. short-load fee (materials only)
$340 – $470
Est. as of 2026-09 — not a live quote
For a pour this size, ready-mix delivery is typically more practical than mixing bags by hand.
Shopping list
- Concrete mix (60 lb bags) Or 176 × 40 lb, 141 × 50 lb or 88 × 80 lb bags. 118 bags
- Ready-mix concrete Alternative to bagged mix; most suppliers have a 1 cu yd order minimum. 2 cu yd
- Compactable gravel sub-base 4 in compacted base beneath the slab. 2.4 tons
- 6x6 welded wire mesh Reinforcement for crack control; not a substitute for engineered rebar on structural slabs. 159 sq ft
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Buy bagged concrete
Pick up bagged mix and reinforcement from a hardware store for smaller pours.
View shopping listAssumptions
- Waste allowance: 10% applied to account for over-excavation and spillage.
- Approx. wet weight: 7,920 lb (4 tons).
- Prices are national-average retail/delivery ranges as of 2026-09, not live quotes.
- Ready-mix orders under 10 cu yd usually carry a short-load fee; the ready-mix range includes a flat $60-$110. Some suppliers charge per yard instead, so ask for the full fee schedule.
Bags or ready-mix for a 12x12 slab, 4 in?
At 1.96 cu yd, the 12x12 sits where bagged concrete and ready-mix cross over in price. For the 12x12, 88 80 lb bags cost about $590 – $826, while 2 cu yd of ready-mix costs about $340 – $470, short-load fee included. Ready-mix wins for this 12x12 by roughly $303 (range midpoints), and nobody has to mix 88 bags by hand.
Is 4 in thick enough for a 12x12 slab?
Foot traffic, patio furniture and a shed all sit fine on a 12x12 poured 4 in thick, the standard for slabs that don't carry vehicles.
Control joints for a 12x12 slab at 4 in
Like any slab, a 4 in 12x12 shrinks while it cures; control joints decide where its cracks go. ACI and PCA guidance spaces joints 24 to 36 times the thickness, which for this 12x12 at 4 in is every 8 to 12 ft, sawn 1 in deep (a quarter of the slab) once the surface holds up to the blade, usually within a day.
On the 12x12 at 4 in, a joint every 10 ft or less means 1 joint each way: 4 panels of about 6 × 6 ft and 24 ft of saw cut.
How much a 12x12 slab 4 in thick weighs
Wet concrete weighs about 150 lb per cubic foot, so the 12x12 pour is about 7,920 lb (4 tons). As bags, the 12x12 is 88 80 lb bags, 7,040 lb in all: about 5 trips in a pickup carrying 1,500 lb a load. For that many trips with the 12x12, check the payload on your truck's door-jamb sticker, or have the store deliver the pallets for a fee.
The 12x12 at 4 in against nearby sizes
Every row uses the same 10% waste and prices as the 12x12 at 4 in; costs are for the concrete only.
| Slab | Cu yd | 60 lb bags | 80 lb bags | Ready-mix order | Bags cost | Ready-mix cost |
|---|---|---|---|---|---|---|
| 10x12 slab, 4 in | 1.63 | 98 | 74 | 1.75 cu yd | $490 – $686 | $305 – $425 |
| 12x12 slab, 4 in (this page) | 1.96 | 118 | 88 | 2 cu yd | $590 – $826 | $340 – $470 |
| 12x16 slab, 4 in | 2.61 | 157 | 118 | 2.75 cu yd | $785 – $1,099 | $445 – $605 |
Questions about a 12x12 slab, 4 in
How many bags of concrete for a 12x12 slab 4 inches thick?
Plan on 52.8 cubic feet for the 12x12, which is 88 80 lb bags, 118 60 lb bags, 141 50 lb or 176 40 lb bags once 10% waste is in.
How many yards of concrete for a 12x12 slab 4 inches thick?
1.96 cubic yards with waste (1.78 without) for a 12x12 at 4 in. Round the 12x12 order to 2 cu yd: plants batch in quarter yards and most won't send less than a yard.
How much does a 12x12 concrete slab 4 inches thick cost?
Concrete alone for the 12x12 runs about $340 – $470 for 2 cu yd of ready-mix delivered, short-load fee included, or $590 – $826 for 118 60 lb bags. Add a 4 in gravel base and wire mesh and the bagged 12x12 plan comes to $730 – $1,053. Labor, forms and finishing for a 12x12 at 4 in come on top of these national ranges (as of 2026-09), which are not quotes.
How much does a 12x12 concrete slab 4 inches thick weigh?
About 7,920 lb (4 tons) of wet concrete for the 12x12, at 150 lb per cubic foot. The 88 80 lb bags for a 12x12 weigh 7,040 lb: about 5 trips in a pickup carrying 1,500 lb a load.
Where do control joints go on a 12x12 slab 4 inches thick?
On a 12x12 at 4 in, every 8 to 12 ft (24 to 36 times the thickness), sawn 1 in deep. On the 12x12 at 4 in, a joint every 10 ft or less means 1 joint each way: 4 panels of about 6 × 6 ft and 24 ft of saw cut.
Limitations
The 12x12 figures at 4 in are material estimates and typical price ranges, not a quote or a structural design. Confirm that 4 in, the reinforcement and the joint layout suit your soil, loads and local code for a 12x12 slab with a qualified professional.