14 by 20 ft slab at 5 inches
Calculate the requirements for a residential slab of 14 ft by 20 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
4.75 yd³
3.634 m³ placed+waste
Order weight
19,250 lb
8,732 kg
80 lb bags
214
6 pallets at 42 bags
60 lb bags
286
0.45 ft³ yield each
Rebar
396.00 ft
24 × 20 ft · 34 × 6 m · 291 lb
Ready-mix vs bags
$784.26
Truck $784.26 · 80 lb bags $1,444.50
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 | 4.32 yd³ | 10% | 4.75 yd³ / 3.634 m³ | USD | $784.26 | 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 | 194.4 bags | 10% | 214 bags | USD | $1,444.50 | Source Spec Material / Tool |
| 60 lb pre-mix bags | 259.3 bags | 10% | 286 bags | USD | $1,544.40 | Source Spec Material / Tool |
| #4 rebar sticks, 20 ft | 24 sticks | 10% | 27 sticks / 34 × 6 m | USD | $378.00 | Source Spec Material / Tool |
| Rebar chairs | 140 crossings | 10% | 154 chairs | USD | $43.12 | Source Spec Material / Tool |
| Tie wire rolls | 140 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
$784.26
0.48 nominal 10 yd³ loads · 1 to order
80 lb bags
$1,444.50
60 lb alternative $1,544.40 · delivery weight 19,250 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 4 in | 3.80 | 2.907 | 172 | 436 | $752.41 | $1,161.00 |
| 5 in | 4.75 | 3.634 | 214 | 436 | $784.26 | $1,444.50 |
| 6 in | 5.70 | 4.361 | 257 | 436 | $941.11 | $1,734.75 |
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: 14 by 20 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 assists in determining the specifications for a residential concrete slab measuring 14 ft by 20 ft with a thickness of 5 inches. The design incorporates #4 rebar spaced at 18 inches, following the guidelines outlined in IRC R506.
Please note that soil design considerations are excluded from this calculation. Always consult a licensed professional engineer for site-specific requirements.
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 and reducing the risk of cracking.
- Why is soil design excluded from this calculation?
- Soil design is site-specific and depends on various factors such as soil type, load-bearing capacity, and moisture content, which are not covered in this general calculator.
- What does IRC R506 cover?
- IRC R506 provides guidelines for the design and construction of concrete slabs on grade, including reinforcement, thickness, and placement.