10 by 18 ft slab at 8 inches
Calculate the specifications for a residential slab measuring 10 ft by 18 ft at 8 in thickness with #4 bars at 18 in spacing. Ensure compliance with IRC R506 guidelines.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
5.60 yd³
4.278 m³ placed+waste
Order weight
22,660 lb
10,278 kg
80 lb bags
252
6 pallets at 42 bags
60 lb bags
336
0.45 ft³ yield each
Rebar
368.00 ft
26 × 20 ft · 26 × 6 m · 270 lb
Ready-mix vs bags
$923.19
Truck $923.19 · 80 lb bags $1,701.00
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 | Source Spec Material / Tool |
|---|---|---|---|---|---|---|
| Ready-mix concrete | 5.09 yd³ | 10% | 5.60 yd³ / 4.278 m³ | USD | $923.19 | 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 | 228.9 bags | 10% | 252 bags | USD | $1,701.00 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 305.2 bags | 10% | 336 bags | USD | $1,814.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 26 sticks | 10% | 29 sticks / 26 × 6 m | USD | $406.00 | Source Spec Material / Tool |
| Rebar chairs | 91 crossings | 10% | 101 chairs | USD | $28.28 | Source Spec Material / Tool |
| Tie wire rolls | 91 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
$923.19
0.56 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,701.00
60 lb alternative $1,814.40 · delivery weight 22,660 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 3.86 | 2.949 | 174 | 405 | $761.37 | $1,174.50 |
| 5 in | 4.29 | 3.281 | 194 | 405 | $708.07 | $1,309.50 |
| 6 in | 4.73 | 3.613 | 213 | 405 | $779.78 | $1,437.75 |
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 18 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 concrete slab measuring 10 ft by 18 ft with a thickness of 8 inches. The slab reinforcement includes #4 bars spaced at 18 inches on center. Please note that soil design considerations are excluded from this calculation.
For compliance, refer to the International Residential Code (IRC) Section R506, which outlines the requirements for concrete slabs in residential construction.
Code reference
IRC R506
Field questions
- What is the purpose of using #4 bars in the slab?
- The #4 bars are used to provide tensile strength to the concrete slab, helping to prevent cracking and improve load distribution.
- Why is soil design excluded from this calculation?
- Soil design is excluded because it requires site-specific analysis and testing to determine the appropriate foundation design based on soil conditions.
- What does IRC R506 cover?
- IRC R506 covers the requirements for the design and construction of concrete slabs, including thickness, reinforcement, and placement.
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