8 by 16 ft slab at 6 inches
Calculate the specifications for an 8 ft by 16 ft residential slab at 6 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
3.50 yd³
2.679 m³ placed+waste
Order weight
14,190 lb
6,436 kg
80 lb bags
158
4 pallets at 42 bags
60 lb bags
211
0.45 ft³ yield each
Rebar
280.00 ft
23 × 20 ft · 23 × 6 m · 206 lb
Ready-mix vs bags
$703.11
Truck $703.11 · 80 lb bags $1,066.50
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 | 3.19 yd³ | 10% | 3.50 yd³ / 2.679 m³ | USD | $578.11 | Source Spec Material / Tool |
| Short-load fee | Under 4 yd³ | — | 1 truck @ 10 yd³ | USD | $125.00 | Source Spec Material / Tool |
| 80 lb pre-mix bags | 143.3 bags | 10% | 158 bags | USD | $1,066.50 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 191.1 bags | 10% | 211 bags | USD | $1,139.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 23 sticks | 10% | 26 sticks / 23 × 6 m | USD | $364.00 | Source Spec Material / Tool |
| Rebar chairs | 66 crossings | 10% | 73 chairs | USD | $20.44 | Source Spec Material / Tool |
| Tie wire rolls | 66 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
$703.11
0.35 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,066.50
60 lb alternative $1,139.40 · delivery weight 14,190 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 2.93 | 2.243 | 132 | 308 | $609.00 | $891.00 |
| 5 in | 3.22 | 2.461 | 145 | 308 | $656.06 | $978.75 |
| 6 in | 3.50 | 2.679 | 158 | 308 | $703.11 | $1,066.50 |
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 16 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 determine the requirements for a residential slab measuring 8 ft by 16 ft with a thickness of 6 inches, reinforced with #4 bars spaced 18 inches apart. Please note that soil design considerations are excluded from this calculation.
For compliance, refer to the International Residential Code (IRC) 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 provide reinforcement to the concrete slab, helping to control cracking and improve structural integrity.
- Why is soil design excluded from this calculation?
- Soil design is a separate consideration that depends on various factors including soil type, load-bearing capacity, and local conditions, which are not addressed in this 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 often should the #4 bars be spaced?
- In this design, the #4 bars should be spaced 18 inches apart to ensure proper reinforcement throughout the slab.