16 by 30 ft slab at 8 inches
Calculate the requirements for a 16 ft by 30 ft residential slab at 8 in thickness with #4 bars at 18 in spacing. Excludes soil design considerations. Complies with IRC R506.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
14.23 yd³
10.881 m³ placed+waste
Order weight
57,640 lb
26,145 kg
80 lb bags
641
16 pallets at 42 bags
60 lb bags
854
0.45 ft³ yield each
Rebar
850.00 ft
53 × 20 ft · 53 × 6 m · 625 lb
Ready-mix vs bags
$2,348.30
Truck $2,348.30 · 80 lb bags $4,326.75
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 | 12.94 yd³ | 10% | 14.23 yd³ / 10.881 m³ | USD | $2,348.30 | 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 | 582.2 bags | 10% | 641 bags | USD | $4,326.75 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 776.3 bags | 10% | 854 bags | USD | $4,611.60 | 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
$2,348.30
1.42 nominal 10 yd³ loads · 2 to order
80 lb bags
$4,326.75
60 lb alternative $4,611.60 · delivery weight 57,640 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.
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Project: 16 by 30 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 helps you determine the specifications for a residential slab measuring 16 ft by 30 ft with a thickness of 8 inches. The design incorporates #4 rebar placed at 18-inch intervals, ensuring adequate reinforcement for structural integrity.
Please note that soil design considerations are excluded from this calculation. For compliance with the International Residential Code (IRC) R506, ensure that all local building codes and regulations are followed.
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 load-bearing capacity.
- Why is soil design excluded from this calculation?
- Soil design is a complex process that requires site-specific analysis. This calculator focuses solely on the concrete slab dimensions and reinforcement.
- What thickness is recommended for a residential slab?
- An 8-inch thickness is commonly recommended for residential slabs to provide adequate strength and durability.
- How do I ensure compliance with IRC R506?
- To ensure compliance, follow the guidelines outlined in IRC R506 regarding slab design, reinforcement, and construction practices.
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