16 by 30 ft slab at 5 inches
Calculate the requirements for a 16 ft by 30 ft residential slab with #4 bars at 18 in spacing. Ensure compliance with IRC R506 while excluding soil design considerations.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
8.15 yd³
6.230 m³ placed+waste
Order weight
33,000 lb
14,969 kg
80 lb bags
367
9 pallets at 42 bags
60 lb bags
489
0.45 ft³ yield each
Rebar
666.00 ft
43 × 20 ft · 43 × 6 m · 489 lb
Ready-mix vs bags
$1,344.44
Truck $1,344.44 · 80 lb bags $2,477.25
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 | 7.41 yd³ | 10% | 8.15 yd³ / 6.230 m³ | USD | $1,344.44 | 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 | 333.3 bags | 10% | 367 bags | USD | $2,477.25 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 444.4 bags | 10% | 489 bags | USD | $2,640.60 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 43 sticks | 10% | 48 sticks / 43 × 6 m | USD | $672.00 | 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
$1,344.44
0.81 nominal 10 yd³ loads · 1 to order
80 lb bags
$2,477.25
60 lb alternative $2,640.60 · delivery weight 33,000 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 6.52 | 4.984 | 294 | 733 | $1,075.56 | $1,984.50 |
| 5 in | 8.15 | 6.230 | 367 | 733 | $1,344.44 | $2,477.25 |
| 6 in | 9.78 | 7.476 | 440 | 733 | $1,613.33 | $2,970.00 |
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 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
When designing a residential slab measuring 16 ft by 30 ft and 5 inches thick, it is essential to incorporate #4 rebar bars placed at 18 inches on center to enhance structural integrity. This design adheres to the International Residential Code (IRC) R506, which provides guidelines for concrete slabs.
Please note that soil design considerations are excluded from this calculation and should be addressed separately by a qualified professional.
Code reference
IRC R506
Field questions
- What is the purpose of using #4 bars in the slab?
- Using #4 bars helps to reinforce the concrete slab, providing additional tensile strength to prevent cracking and improve overall durability.
- Why is soil design excluded from this calculation?
- Soil design is a critical aspect that depends on specific site conditions and should be evaluated by a qualified engineer to ensure proper load-bearing capacity.
- What thickness is recommended for a residential slab?
- A thickness of 5 inches is commonly recommended for residential slabs, providing a balance between strength and material efficiency.
- What does IRC R506 cover?
- IRC R506 outlines the requirements for concrete slabs, including design, reinforcement, and construction practices to ensure safety and structural integrity.
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