12 by 24 ft slab at 6 inches
Calculate the requirements for a residential slab measuring 12 ft by 24 ft at 6 in thickness with #4 bars at 18 in spacing. Excludes soil design considerations. Compliant with IRC R506.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
7.25 yd³
5.544 m³ placed+waste
Order weight
29,370 lb
13,322 kg
80 lb bags
327
8 pallets at 42 bags
60 lb bags
436
0.45 ft³ yield each
Rebar
564.00 ft
43 × 20 ft · 43 × 6 m · 414 lb
Ready-mix vs bags
$1,196.56
Truck $1,196.56 · 80 lb bags $2,207.25
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 | Source Spec Material / Tool |
|---|---|---|---|---|---|---|
| Ready-mix concrete | 6.59 yd³ | 10% | 7.25 yd³ / 5.544 m³ | USD | $1,196.56 | Source Spec Material / Tool |
| Short-load fee | Full load | — | 1 truck @ 10 yd³ | USD | $0.00 | Source Spec Material / Tool |
| 80 lb pre-mix bags | 296.7 bags | 10% | 327 bags | USD | $2,207.25 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 395.6 bags | 10% | 436 bags | USD | $2,354.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 43 sticks | 10% | 48 sticks / 43 × 6 m | USD | $672.00 | Source Spec Material / Tool |
| Rebar chairs | 153 crossings | 10% | 169 chairs | USD | $47.32 | Source Spec Material / Tool |
| Tie wire rolls | 153 ties | 10% | 1 rolls | USD | $8.00 | Source Spec Material / Tool |
Source links open a product search on the Amazon storefront for the selected currency. SiteSpecCalc may earn a commission. The link does not change the quantities above.
Ready-mix truck
$1,196.56
0.73 nominal 10 yd³ loads · 1 to order
80 lb bags
$2,207.25
60 lb alternative $2,354.40 · delivery weight 29,370 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 5.76 | 4.402 | 260 | 620 | $950.07 | $1,755.00 |
| 5 in | 6.50 | 4.973 | 293 | 620 | $1,073.31 | $1,977.75 |
| 6 in | 7.25 | 5.544 | 327 | 620 | $1,196.56 | $2,207.25 |
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 by 24 ft slab at 6 inches
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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
This calculator helps you determine the specifications for a residential concrete slab measuring 12 ft by 24 ft with a thickness of 6 inches. The design incorporates #4 rebar placed at 18-inch intervals, ensuring structural integrity.
Please note that soil design considerations are excluded from this calculation. For a complete assessment, consult a licensed engineer for site-specific soil analysis.
Code reference
IRC R506 - Concrete Floors on Ground
Field questions
- What is the purpose of using #4 bars in the slab?
- The #4 bars provide reinforcement to the concrete slab, helping to control cracking and improve load-bearing capacity.
- Why is soil design excluded from this calculator?
- Soil design is site-specific and requires a thorough analysis of the soil conditions, which is beyond the scope of this calculator.
- What does IRC R506 cover?
- IRC R506 provides guidelines for the design and construction of concrete floors on the ground, including thickness, reinforcement, and placement.