Concrete Slab, Rebar, and Bag Calculator
Size a slab-on-ground, optional turn-down edge, and a rebar mat. Compare bagged concrete with a ready-mix truck before you order.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
5.43 yd³
4.153 m³ placed+waste
Order weight
22,000 lb
9,979 kg
80 lb bags
245
6 pallets at 42 bags
60 lb bags
326
0.45 ft³ yield each
Rebar
560.00 ft
28 × 20 ft · 56 × 6 m · 411 lb
Ready-mix vs bags
$896.30
Truck $896.30 · 80 lb bags $1,653.75
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 | 4.94 yd³ | 10% | 5.43 yd³ / 4.153 m³ | USD | $896.30 |
| Short-load fee | Full load | — | 1 truck @ 10 yd³ | USD | $0.00 |
| 80 lb pre-mix bags | 222.2 bags | 10% | 245 bags | USD | $1,653.75 |
| 60 lb pre-mix bags | 296.3 bags | 10% | 326 bags | USD | $1,760.40 |
| #4 rebar sticks, 20 ft | 28 sticks | 10% | 31 sticks / 56 × 6 m | USD | $434.00 |
| Rebar chairs | 196 crossings | 10% | 216 chairs | USD | $60.48 |
| Tie wire rolls | 196 ties | 10% | 1 rolls | USD | $8.00 |
Ready-mix truck
$896.30
0.54 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,653.75
60 lb alternative $1,760.40 · delivery weight 22,000 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 5.43 | 4.153 | 245 | 616 | $896.30 | $1,653.75 |
| 5 in | 6.79 | 5.191 | 306 | 616 | $1,120.37 | $2,065.50 |
| 6 in | 8.15 | 6.230 | 367 | 616 | $1,344.44 | $2,477.25 |
| 8 in | 10.86 | 8.306 | 489 | 616 | $1,792.59 | $3,300.75 |
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.
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Project: Concrete Slab, Rebar, and Bag Calculator
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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
Volume is length times width times thickness, plus the extra concrete in a thickened edge below the slab. Bag counts use 0.60 cubic feet per 80 lb bag and 0.45 cubic feet per 60 lb bag. Rebar quantity is an on-center grid with a bar at each end of the layout, and two continuous edge bars when the turn-down is on. Waste is applied to the order quantity, not to the placed volume.
Enter the plant price for the PSI you selected. A short-load fee is suggested under 4 cubic yards and can be edited or set to zero. This is an estimate of material quantity, not a soil, frost, or structural design.
Code reference
IRC R506.1 minimum slab-on-ground thickness, ACI 318 cover and reinforcement practice, and ACI 302 guidance for slabs on ground. Confirm the adopted local edition.
Field questions
- How does the calculator convert cubic feet to cubic yards?
- Placed volume in cubic feet is divided by 27. The order quantity multiplies that volume by the selected waste factor before the yard, meter, and bag conversions.
- Does a thicker edge add concrete that is already inside the slab?
- Only the depth below the slab thickness is added, and the corner squares of the footing band are counted once. The slab rectangle already includes the top of the edge.
- Can I use the bag count as a structural specification?
- No. PSI, thickness, and rebar size still have to be accepted by the local building official and, where required, a licensed engineer.