10 by 30 ft slab at 8 inches
Calculate the requirements for a residential slab measuring 10 ft by 30 ft at 8 in thickness with #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
9.18 yd³
7.019 m³ placed+waste
Order weight
37,180 lb
16,865 kg
80 lb bags
414
10 pallets at 42 bags
60 lb bags
551
0.45 ft³ yield each
Rebar
580.00 ft
43 × 20 ft · 45 × 6 m · 426 lb
Ready-mix vs bags
$1,514.74
Truck $1,514.74 · 80 lb bags $2,794.50
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 | 8.35 yd³ | 10% | 9.18 yd³ / 7.019 m³ | USD | $1,514.74 | 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 | 375.6 bags | 10% | 414 bags | USD | $2,794.50 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 500.7 bags | 10% | 551 bags | USD | $2,975.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 43 sticks | 10% | 48 sticks / 45 × 6 m | USD | $672.00 | Source Spec Material / Tool |
| Rebar chairs | 147 crossings | 10% | 162 chairs | USD | $45.36 | Source Spec Material / Tool |
| Tie wire rolls | 147 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
$1,514.74
0.92 nominal 10 yd³ loads · 1 to order
80 lb bags
$2,794.50
60 lb alternative $2,975.40 · delivery weight 37,180 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 6.14 | 4.693 | 277 | 638 | $1,012.81 | $1,869.75 |
| 5 in | 6.90 | 5.274 | 311 | 638 | $1,138.30 | $2,099.25 |
| 6 in | 7.66 | 5.856 | 345 | 638 | $1,263.78 | $2,328.75 |
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.
Contractor sign-off
Project: 10 by 30 ft slab at 8 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 to assist in the preliminary design of a residential slab measuring 10 ft by 30 ft with a thickness of 8 inches. The specified reinforcement consists of #4 bars placed at 18 inches on center.
Please note that soil design considerations are excluded from this calculation, and it is essential to consult with a licensed engineer for a comprehensive design that meets local codes and site-specific conditions.
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 tensile strength to the concrete slab, helping to control cracking and improve the overall structural integrity.
- Why is soil design excluded from this calculator?
- Soil design is site-specific and requires a geotechnical analysis to determine the appropriate foundation design based on soil conditions.
- What does IRC R506 cover?
- IRC R506 provides guidelines for the design and construction of concrete floors on the ground, including thickness, reinforcement, and other requirements.
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