What is the purpose of using #4 bars in the slab?

Using #4 bars provides structural reinforcement to the concrete slab, helping to prevent cracking and improve load-bearing capacity.

Why is soil design excluded from this calculation?

Soil design is excluded because it requires specific analysis based on site conditions, which should be performed by a qualified engineer.

What does IRC R506 cover?

IRC R506 outlines the requirements for concrete slabs, including thickness, reinforcement, and placement to ensure structural integrity.

16 by 14 ft slab at 5 inches

Calculate the specifications for a residential slab measuring 16 ft by 14 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

3.80 yd³

2.907 m³ placed+waste

Order weight

15,400 lb

6,985 kg

80 lb bags

172

5 pallets at 42 bags

60 lb bags

229

0.45 ft³ yield each

Rebar

314.00 ft

21 × 20 ft · 21 × 6 m · 231 lb

Ready-mix vs bags

$752.41

Truck $752.41 · 80 lb bags $1,161.00

Slab footprint and rebar gridLive scaled blueprint

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.

Bill of materials and shopping list
Item	Net	Waste	Order	Unit price	Line total	Source Spec Material / Tool
Ready-mix concrete	3.46 yd³	10%	3.80 yd³ / 2.907 m³	USD	$627.41	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	155.6 bags	10%	172 bags	USD	$1,161.00	Source Spec Material / Tool
60 lb pre-mix bags	207.4 bags	10%	229 bags	USD	$1,236.60	Source Spec Material / Tool
#4 rebar sticks, 20 ft	21 sticks	10%	24 sticks / 21 × 6 m	USD	$336.00	Source Spec Material / Tool
Rebar chairs	110 crossings	10%	121 chairs	USD	$33.88	Source Spec Material / Tool
Tie wire rolls	110 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

$752.41

0.38 nominal 10 yd³ loads · 1 to order

80 lb bags

$1,161.00

60 lb alternative $1,236.60 · delivery weight 15,400 lb

Side-by-side thickness comparison at the same footprint
Thickness	Order yd³	Order m³	80 lb bags	Rebar ft	Ready-mix	80 lb cost
4 in	3.04	2.326	137	345	$626.93	$924.75
5 in	3.80	2.907	172	345	$752.41	$1,161.00
6 in	4.56	3.489	206	345	$752.89	$1,390.50

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: 16 by 14 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 requirements for a residential concrete slab measuring 16 ft by 14 ft with a thickness of 5 inches. The design includes #4 rebar placed at 18 inches on center, ensuring adequate reinforcement.

Please note that soil design considerations are excluded from this calculation. It is essential to consult a qualified engineer for soil analysis and site-specific conditions.

Code reference

IRC R506 - Concrete Slabs

Field questions

What is the purpose of using #4 bars in the slab?: Using #4 bars provides structural reinforcement to the concrete slab, helping to prevent cracking and improve load-bearing capacity.
Why is soil design excluded from this calculation?: Soil design is excluded because it requires specific analysis based on site conditions, which should be performed by a qualified engineer.
What does IRC R506 cover?: IRC R506 outlines the requirements for concrete slabs, including thickness, reinforcement, and placement to ensure structural integrity.