12×20 Slab at 6 Inches: Rebar, Bags, and Truck
A 12 by 20 ft pad at 6 in, with the thickness table repeating the takeoff at the other standard depths.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
4.89 yd³
3.738 m³ placed+waste
Order weight
19,800 lb
8,981 kg
80 lb bags
220
6 pallets at 42 bags
60 lb bags
294
0.45 ft³ yield each
Rebar
348.00 ft
23 × 20 ft · 32 × 6 m · 256 lb
Ready-mix vs bags
$806.67
Truck $806.67 · 80 lb bags $1,485.00
Grid lines are equalized so the drawing stays readable. The order count uses on-center spacing with a bar at each end of the layout, then holds concrete cover in the field.
| Item | Net | Waste | Order | Unit price | Line total |
|---|---|---|---|---|---|
| Ready-mix concrete | 4.44 yd³ | 10% | 4.89 yd³ / 3.738 m³ | USD | $806.67 |
| Short-load fee | Full load | — | 1 truck @ 10 yd³ | USD | $0.00 |
| 80 lb pre-mix bags | 200.0 bags | 10% | 220 bags | USD | $1,485.00 |
| 60 lb pre-mix bags | 266.7 bags | 10% | 294 bags | USD | $1,587.60 |
| #4 rebar sticks, 20 ft | 23 sticks | 10% | 26 sticks / 32 × 6 m | USD | $364.00 |
| Rebar chairs | 126 crossings | 10% | 139 chairs | USD | $38.92 |
| Tie wire rolls | 126 ties | 10% | 1 rolls | USD | $8.00 |
Ready-mix truck
$806.67
0.49 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,485.00
60 lb alternative $1,587.60 · delivery weight 19,800 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 3.26 | 2.492 | 147 | 383 | $662.78 | $992.25 |
| 5 in | 4.07 | 3.115 | 184 | 383 | $672.22 | $1,242.00 |
| 6 in | 4.89 | 3.738 | 220 | 383 | $806.67 | $1,485.00 |
Show the deterministic formula
Slab ft³ = L × W × thickness ÷ 12. Thickened-edge extra = footing band × (footing depth − slab thickness), with corner squares counted once.
yd³ = ft³ ÷ 27. m³ = ft³ × 0.0283168. Weight uses 150 lb/ft³, then the header converts that pound total at 1 lb = 0.45359237 kg. 80 lb bags yield 0.6 ft³ and 60 lb bags yield 0.45 ft³. Currency changes the price labels only.
Bars across a span = floor(span ÷ spacing) + 1. Order sticks = that count, plus 10, 5, or 15 percent waste, cut from 20 ft and 6 m stock. Chairs = one per grid intersection.
Contractor sign-off
Project: 12×20 Slab at 6 Inches: Rebar, Bags, and Truck
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.
Engineering notes
A 12 by 20 ft rectangle at 6 in is about 4.44 cubic yards before waste. This page adds 10 percent waste, prices 4,000 PSI ready-mix against 80 lb and 60 lb bags, and lays #4 bar at 18 in on center. The comparison table repeats the same footprint at 4, 5, and 6 in so the extra inch of thickness is only extra volume, not a different grid. Soil bearing, vapor retarder, and joints are not designed here.
Code reference
IRC R506.1 sets a 3.5 in minimum for concrete slab-on-ground floors. Reinforcement cover and spacing follow ACI 318 practice and the local inspector. This quantity takeoff is not a soils or structural design.
Field questions
- How many cubic yards is a 12 by 20 slab at 6 in before waste?
- Length times width times thickness in feet, divided by 27, is about 4.44 cubic yards. The order line then applies the waste factor on the page.
- Does the rebar count change when the slab gets thicker?
- No. The grid follows the length, width, and spacing. Thickness changes volume, weight, bags, and the ready-mix price.
- When is a truck cheaper than bags?
- Compare the ready-mix line, including any short-load fee under 4 yards, with the 80 lb bag line. Both use the prices typed on the page.
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