8 by 24 ft slab at 6 inches
Calculate the specifications for a residential slab measuring 8 ft by 24 ft with a thickness of 6 in and #4 bars at 18 in spacing. Ensure compliance with IRC R506 standards.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
5.13 yd³
3.925 m³ placed+waste
Order weight
20,790 lb
9,430 kg
80 lb bags
231
6 pallets at 42 bags
60 lb bags
308
0.45 ft³ yield each
Rebar
408.00 ft
37 × 20 ft · 37 × 6 m · 300 lb
Ready-mix vs bags
$847.00
Truck $847.00 · 80 lb bags $1,559.25
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 | 4.67 yd³ | 10% | 5.13 yd³ / 3.925 m³ | USD | $847.00 | 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 | 210.0 bags | 10% | 231 bags | USD | $1,559.25 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 280.0 bags | 10% | 308 bags | USD | $1,663.20 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 37 sticks | 10% | 41 sticks / 37 × 6 m | USD | $574.00 | Source Spec Material / Tool |
| Rebar chairs | 102 crossings | 10% | 113 chairs | USD | $31.64 | Source Spec Material / Tool |
| Tie wire rolls | 102 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
$847.00
0.51 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,559.25
60 lb alternative $1,663.20 · delivery weight 20,790 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 4.24 | 3.239 | 191 | 449 | $699.11 | $1,289.25 |
| 5 in | 4.69 | 3.582 | 211 | 449 | $773.06 | $1,424.25 |
| 6 in | 5.13 | 3.925 | 231 | 449 | $847.00 | $1,559.25 |
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: 8 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 is designed for residential slab foundations, specifically for slabs measuring 8 ft by 24 ft with a thickness of 6 inches. The reinforcement is provided using #4 bars spaced at 18 inches on center. Please note that soil design considerations are excluded from this calculation.
For compliance with the International Residential Code (IRC) R506, ensure that all local building codes and regulations are followed during construction.
Code reference
IRC R506
Field questions
- What is the purpose of using #4 bars in the slab?
- The #4 bars provide tensile strength to the concrete slab, helping to resist cracking and improve overall structural integrity.
- Why is soil design excluded from this calculation?
- Soil design is excluded because it requires site-specific analysis and testing, which varies based on local conditions and is not covered in this general calculator.
- What thickness is recommended for a residential slab?
- A thickness of 6 inches is commonly recommended for residential slabs, providing adequate support for typical loads.
- How do I ensure compliance with IRC R506?
- To ensure compliance with IRC R506, follow the specified guidelines for slab thickness, reinforcement, and other construction practices outlined in the code.