16 by 30 ft slab at 6 inches
Calculate the specifications for a residential slab measuring 16 ft by 30 ft at 6 in thick 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
11.57 yd³
8.846 m³ placed+waste
Order weight
46,860 lb
21,255 kg
80 lb bags
521
13 pallets at 42 bags
60 lb bags
695
0.45 ft³ yield each
Rebar
850.00 ft
53 × 20 ft · 53 × 6 m · 625 lb
Ready-mix vs bags
$1,909.11
Truck $1,909.11 · 80 lb bags $3,516.75
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 | 10.52 yd³ | 10% | 11.57 yd³ / 8.846 m³ | USD | $1,909.11 | Source Spec Material / Tool |
| Short-load fee | Full load | — | 2 truck @ 10 yd³ | USD | $0.00 | Source Spec Material / Tool |
| 80 lb pre-mix bags | 473.3 bags | 10% | 521 bags | USD | $3,516.75 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 631.1 bags | 10% | 695 bags | USD | $3,753.00 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 53 sticks | 10% | 59 sticks / 53 × 6 m | USD | $826.00 | Source Spec Material / Tool |
| Rebar chairs | 231 crossings | 10% | 255 chairs | USD | $71.40 | Source Spec Material / Tool |
| Tie wire rolls | 231 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
$1,909.11
1.16 nominal 10 yd³ loads · 2 to order
80 lb bags
$3,516.75
60 lb alternative $3,753.00 · delivery weight 46,860 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 8.91 | 6.811 | 401 | 935 | $1,469.93 | $2,706.75 |
| 5 in | 10.24 | 7.829 | 461 | 935 | $1,689.52 | $3,111.75 |
| 6 in | 11.57 | 8.846 | 521 | 935 | $1,909.11 | $3,516.75 |
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: 16 by 30 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 assists in determining the requirements for a residential concrete slab measuring 16 ft by 30 ft and 6 inches thick, reinforced with #4 bars spaced at 18 inches on center. Please note that soil design considerations are excluded from this calculation.
Ensure that your design complies with the International Residential Code (IRC) R506 for concrete floors and slabs.
Code reference
IRC R506
Field questions
- What is the purpose of reinforcing bars in a concrete slab?
- Reinforcing bars, or rebar, are used in concrete slabs to improve tensile strength and help prevent cracking, ensuring the slab can withstand loads and environmental factors.
- Why is soil design excluded from this calculation?
- Soil design is a complex process that involves evaluating the soil's bearing capacity and other geotechnical factors. This calculator focuses solely on the concrete slab design and reinforcement.
- What does IRC R506 cover?
- IRC R506 provides guidelines for the design and construction of concrete floors and slabs, including requirements for thickness, reinforcement, and curing.