16x24 Concrete Slab: Cost, Yards & Bags of Concrete
Quick answer: a 16 × 24 ft slab (384 sq ft) 4 inches thick needs 4.74 yd³ of concrete, 5.21 yd³ with 10% waste (order 5.25 yd³ of ready-mix) or 235 bags of 80-lb mix. Installed, it costs about $2,710 – $4,880 ($7.00 – $13.00 per sq ft); DIY materials run $1,080 – $1,690.
A 16 × 24 ft slab (384 sq ft) is the floor for a large storage building, a backyard workshop or a one-car garage-style shed. It is usually above the size most towns let you build without a permit, so the inspector may set the edge detail; the cost section shows both a floating slab and the thickened-edge add-on.
Concrete for a 16x24 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) | 4.74 yd³ | 5.21 yd³ | 5.25 yd³ | 235 | 313 | 470 | $2,710–$4,880 |
| 5 in | 5.93 yd³ | 6.52 yd³ | 6.75 yd³ | 294 | 392 | 587 | $2,910–$5,120 |
| 6 in | 7.11 yd³ | 7.82 yd³ | 8 yd³ | 352 | 470 | 704 | $3,100–$5,360 |
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) | 4.74 yd³ | 214 |
| 5% | 4.98 yd³ | 224 |
| 10% | 5.21 yd³ | 235 |
| 15% | 5.45 yd³ | 246 |
Bags or a Ready-Mix Truck?
| Option | What you buy | Concrete bill |
|---|---|---|
| 80-lb bags | 235 bags at $6.50 + mixer rental $75 | $1,603 |
| Ready-mix | 5.25 yd³ at $150 + $120 delivery | $908 |
Ready-mix, without question. 235 bags would cost $1,603 and take about 9 hours of mixing, far longer than concrete stays workable, so the slab would end up with cold joints. Ready-mix trucks bring it as fast as the crew can place it. Try your own prices in the bags vs. ready-mix calculator.
What a 16x24 Slab Costs
| Line item (4 in slab) | Basis | Cost |
|---|---|---|
| Ready-mix concrete + delivery | 5.21 yd³ at $150 + $120 | $902 |
| Forms | 80 lin ft at $2.20 | $176 |
| Vapor barrier | 384 sq ft at $0.35 | $134 |
| #4 rebar at 18 in | 384 sq ft at $1.25 | $480 |
| Broom finish | 384 sq ft at $0.75 | $288 |
| Labor (place & finish) | 384 sq ft at $5.00 | $1,920 |
| Direct cost | Before overhead and profit | $3,901 |
- Installed price: $2,710 – $4,880. 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 $540 – $1,270 more.
- Thickened edge (12 in wide, 12–18 in deep) if the building sits on the slab: 2.1–3.6 yd³ more concrete, about $310 – $540, 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 16 × 24 ft Slab
| Concrete | 5.25 yd³ ready-mix, or 235 × 80-lb / 470 × 40-lb bags |
|---|---|
| Gravel base (4 in compacted) | 5.45 yd³, about 7.6 tons |
| Forms | 8 × 2x4 boards 12 ft long, 32 stakes, 64 screws (80 lin ft) |
| Rebar (#4 at 18 in) | 557 lin ft = 28 × 20-ft sticks, 54 chairs |
| Or wire mesh (6x6) | 12 sheets of 5 × 10 ft, about $144 – $240 |
| Vapor barrier | 384 sq ft plus 6 in laps |
| Control joints | 6 panels of about 8 × 8 ft: 56 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 |
- Over 200 sq ft almost every town wants a building permit, and in frost areas a thickened edge or footing below the frost line.
- If it will be heated or finished inside, put a vapor barrier under the slab now.
- Leave a 2-ft-wide apron at the door if you will drive equipment in.
Pour Day for a 16x24 Slab
- Crew time: about 13 crew-hours to set forms, place, finish and cut joints (0.035 h per sq ft for a broom finish).
- Trucks: 5.25 yd³ is 1 truck, about 26–42 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 16x24 Slab
The calculator below starts at 16 × 24 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.
16x24 Slab Questions
About $2,710 to $4,880 installed for a 4-inch slab with forms, a broom finish and labor ($7.00 to $13.00 per sq ft), at U.S. average prices. DIY materials run about $1,080 to $1,690. Site prep and a gravel base add about $540 to $1,270.
At 4 inches thick with 10% waste: 235 bags of 80-lb mix, 313 bags of 60-lb mix or 470 bags of 40-lb mix. At 6 inches: 352 bags of 80-lb mix.
At 4 inches, 4.74 cubic yards (order 5.25 with waste); at 5 inches, 5.93 (order 6.75); at 6 inches, 7.11 (order 8.00). Ready-mix is sold in quarter yards, so round up.
Ready-mix. 5.25 yards delivered costs about $908, while 235 bags would cost about $1,603 and take roughly 9 hours of mixing. Bags only win below about 1.3 cubic yards.
A #4 grid at 18 inches each way needs about 557 linear feet of bar including laps: 28 twenty-foot sticks and about 54 chairs. Welded wire mesh instead takes 12 sheets of 5 x 10 ft.
At 4 inches thick it is 4.74 cubic yards net, 5.21 with waste, so order 5.25 yards. At 6 inches it is 7.11 yards net.