12x16 Concrete Slab: Cost, Yards & Bags of Concrete
Quick answer: a 12 × 16 ft slab (192 sq ft) 4 inches thick needs 2.37 yd³ of concrete, 2.61 yd³ with 10% waste (order 2.75 yd³ of ready-mix) or 118 bags of 80-lb mix. Installed, it costs about $1,450 – $2,560 ($7.50 – $13.50 per sq ft); DIY materials run $630 – $940.
A 12 × 16 ft slab is the classic backyard workshop and large-shed size: 192 sq ft, room for a workbench along one wall and a mower along the other. At 4 in thick it takes 2.61 yd³ with waste, so a small ready-mix load usually beats 118 bags on both price and labor.
Concrete for a 12x16 Slab at 4, 5 and 6 Inches
| Thickness | Net volume | With 10% waste | Ready-mix order | 80-lb bags | 60-lb bags | 40-lb bags | Installed |
|---|---|---|---|---|---|---|---|
| 4 in (typical) | 2.37 yd³ | 2.61 yd³ | 2.75 yd³ | 118 | 157 | 235 | $1,450–$2,560 |
| 5 in | 2.96 yd³ | 3.26 yd³ | 3.5 yd³ | 147 | 196 | 294 | $1,550–$2,680 |
| 6 in | 3.56 yd³ | 3.91 yd³ | 4 yd³ | 176 | 235 | 352 | $1,650–$2,800 |
How Much Extra to Order
The table above adds 10%, the usual allowance for a formed slab on a graded base. Pick less only for rigid forms on a laser-flat base, more for soft or uneven ground:
| Waste allowance (4 in slab) | Concrete | 80-lb bags |
|---|---|---|
| 0% (exact volume) | 2.37 yd³ | 107 |
| 5% | 2.49 yd³ | 112 |
| 10% | 2.61 yd³ | 118 |
| 15% | 2.73 yd³ | 123 |
Bags or a Ready-Mix Truck?
| Option | What you buy | Concrete bill |
|---|---|---|
| 80-lb bags | 118 bags at $6.50 + mixer rental $75 | $842 |
| Ready-mix | 2.75 yd³ at $150 + $120 delivery + $140 short-load fee | $673 |
Ready-mix is $170 cheaper here and saves about 4.7 hours of mixing 118 bags. Bags only win below about 1.3 yd³, once the delivery and short-load fees are counted. Try your own prices in the bags vs. ready-mix calculator.
What a 12x16 Slab Costs
| Line item (4 in slab) | Basis | Cost |
|---|---|---|
| Ready-mix concrete + delivery | 2.61 yd³ at $150 + $120 | $511 |
| Forms | 56 lin ft at $2.20 | $123 |
| Vapor barrier | 192 sq ft at $0.35 | $67 |
| #4 rebar at 18 in | 192 sq ft at $1.25 | $240 |
| Broom finish | 192 sq ft at $0.75 | $144 |
| Labor (place & finish) | 192 sq ft at $5.00 | $960 |
| Direct cost | Before overhead and profit | $2,046 |
- Installed price: $1,450 – $2,560. The low end is a plain slab with lower-cost labor; the high end is the full scope above plus 25% contractor overhead and profit.
- Site prep and gravel base (excavation and 4 in of compacted stone): about $270 – $630 more.
- Thickened edge (12 in wide, 12–18 in deep) if the building sits on the slab: 1.4–2.5 yd³ more concrete, about $210 – $370, plus trenching and two #4 bars around the edge.
- Permit, where one is needed: about $50 – $350.
Have a contractor's price? Put it into the concrete quote checker, or compare two or three bids side by side there.
Materials List for a 12 × 16 ft Slab
| Concrete | 2.75 yd³ ready-mix, or 118 × 80-lb / 235 × 40-lb bags |
|---|---|
| Gravel base (4 in compacted) | 2.73 yd³, about 3.8 tons |
| Forms | 6 × 2x4 boards 12 ft long, 22 stakes, 44 screws (56 lin ft) |
| Rebar (#4 at 18 in) | 276 lin ft = 14 × 20-ft sticks, 30 chairs |
| Or wire mesh (6x6) | 6 sheets of 5 × 10 ft, about $72 – $120 |
| Vapor barrier | 192 sq ft plus 6 in laps |
| Control joints | 4 panels of about 8 × 6 ft: 28 lin ft of saw cut, 1 in deep |
Recommended Specs for a Shed Floor
| Thickness | 4 in; thicken the edge to 8-12 in under the walls in frost country, or follow your permit |
|---|---|
| Strength | 3,000 PSI; 3,500 PSI air-entrained where it freezes |
| Base | 4 to 6 in of compacted crushed stone |
| Reinforcement | 6x6 wire mesh, or #4 rebar at 18 in if a mower, ATV or car will park inside |
| Anchors | 1/2 in J-bolts in the wet concrete, 1-3/4 in in from the edge, about every 4-6 ft and within 12 in of each corner |
- If the shed will be a workshop, plan outlets and any floor-mounted equipment before the pour; a sleeve under the slab for a power feed costs a few dollars now.
- Many towns cap permit-free sheds at 120 or 200 sq ft, and a 12 × 16 is 192 sq ft, so check before you build.
- Use #4 rebar at 18 in if you will park a tractor or roll heavy tools; mesh is fine for storage only.
Pour Day for a 12x16 Slab
- Crew time: about 7 crew-hours to set forms, place, finish and cut joints (0.035 h per sq ft for a broom finish).
- Trucks: 2.75 yd³ is 1 truck, about 14–22 minutes of unloading in total. Concrete must be placed within 90 minutes of batching.
- Reach: a truck chute reaches about 15–20 ft, enough for this slab if the truck can park beside it. If it can't, budget wheelbarrows or a line pump.
- Joints: saw-cut 4–12 hours after finishing with a wet saw, or 1–4 hours with an early-entry saw.
- Curing: foot traffic after 24–48 hours, cars after 7 days, full strength at 28 days.
Price Your Own 12x16 Slab
The calculator below starts at 12 × 16 ft, 4 inches. Change the thickness, finish or reinforcement, pick your state for local prices, and the Live Estimate updates with a blueprint of the joint and rebar layout.
Concrete Slab Cost & Volume Estimator
Precision multi-layer project budgeting: Materials, Sub-Base, Reinforcement, Labor & Equipment
Picking a location sets the ready-mix, excavation and labor rates below to that area's typical level. You can still type your own local prices afterwards. Slab prices by state.
Closer spacing uses more steel and raises the rebar cost.
Not charged when bagged concrete is selected.
A scaled plan of your slab: rebar grid at the spacing you chose, support chairs about every 3 to 4 ft, and the recommended control-joint saw cuts (2.5 times the thickness in inches, in feet, capped at 15 ft). It redraws as you change the inputs.
| Scope Item / Material Description | Amount |
|---|
Enter the total your contractor quoted. We compare it with a benchmark for the same slab and scope you set in the calculator: materials at your entered prices plus labor at the regional standard rate, before any overhead or profit. Make sure the calculator scope (base, rebar, finish, pump, demolition) matches what the bid includes.
Optional: enter the bid's line items to see where the markup sits
Enter the forecast for pour day. The check follows ACI 306R (cold weather) and ACI 305R (hot weather) and estimates the surface evaporation rate that drives plastic shrinkage cracking.
12x16 Slab Questions
About $1,450 to $2,560 installed for a 4-inch slab with forms, a broom finish and labor ($7.50 to $13.50 per sq ft), at U.S. average prices. DIY materials run about $630 to $940. Site prep and a gravel base add about $270 to $630.
At 4 inches thick with 10% waste: 118 bags of 80-lb mix, 157 bags of 60-lb mix or 235 bags of 40-lb mix. At 6 inches: 176 bags of 80-lb mix.
At 4 inches, 2.37 cubic yards (order 2.75 with waste); at 5 inches, 2.96 (order 3.50); at 6 inches, 3.56 (order 4.00). Ready-mix is sold in quarter yards, so round up.
Ready-mix. 2.75 yards delivered costs about $673, while 118 bags would cost about $842 and take roughly 5 hours of mixing. Bags only win below about 1.3 cubic yards.
A #4 grid at 18 inches each way needs about 276 linear feet of bar including laps: 14 twenty-foot sticks and about 30 chairs. Welded wire mesh instead takes 6 sheets of 5 x 10 ft.
Often yes: at 192 sq ft it is over the 120 sq ft exemption many towns use, though some exempt up to 200 sq ft. Check with your building department; zoning setbacks apply either way.