8 by 16 ft slab at 5 inches
Calculate the requirements for a residential slab measuring 8 ft by 16 ft at 5 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
2.17 yd³
1.661 m³ placed+waste
Order weight
8,800 lb
3,992 kg
80 lb bags
98
3 pallets at 42 bags
60 lb bags
131
0.45 ft³ yield each
Rebar
184.00 ft
17 × 20 ft · 17 × 6 m · 135 lb
Ready-mix vs bags
$483.52
Truck $483.52 · 80 lb bags $661.50
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 | 1.98 yd³ | 10% | 2.17 yd³ / 1.661 m³ | USD | $358.52 | 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 | 88.9 bags | 10% | 98 bags | USD | $661.50 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 118.5 bags | 10% | 131 bags | USD | $707.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 17 sticks | 10% | 19 sticks / 17 × 6 m | USD | $266.00 | 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
$483.52
0.22 nominal 10 yd³ loads · 1 to order
80 lb bags
$661.50
60 lb alternative $707.40 · delivery weight 8,800 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 1.74 | 1.329 | 79 | 202 | $411.81 | $533.25 |
| 5 in | 2.17 | 1.661 | 98 | 202 | $483.52 | $661.50 |
| 6 in | 2.61 | 1.994 | 118 | 202 | $555.22 | $796.50 |
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 5 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 8 ft by 16 ft with a thickness of 5 inches. The use of #4 rebar at 18-inch spacing is specified for reinforcement.
Please note that soil design considerations are excluded from this calculation. It is essential to consult a licensed engineer for comprehensive design and 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 tensile strength to the concrete slab, helping to prevent cracking and ensuring structural integrity.
- Why is soil design excluded from this calculation?
- Soil design is a critical factor that varies by location and conditions. It is recommended to consult a licensed engineer for site-specific soil analysis.
- What does IRC R506 cover?
- IRC R506 outlines the requirements for concrete floors on the ground, including thickness, reinforcement, and construction practices to ensure durability and safety.
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