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 preventing cracking.

Why is soil design excluded from this calculation?

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

What is the significance of following IRC R506?

Following IRC R506 ensures that your slab design meets the minimum safety and performance standards for residential construction.

14 by 14 ft slab at 5 inches

Calculate the requirements for a 14 ft x 14 ft residential slab with #4 bars at 18 in spacing. Ensure compliance with IRC R506. Soil design considerations are excluded.

Formula SSC-2026.1

Formula SSC-2026.1 · 4,000 PSI

Order volume

3.33 yd³

2.544 m³ placed+waste

Order weight

13,475 lb

6,112 kg

80 lb bags

150

4 pallets at 42 bags

60 lb bags

200

0.45 ft³ yield each

Rebar

280.00 ft

20 × 20 ft · 20 × 6 m · 206 lb

Ready-mix vs bags

$673.98

Truck $673.98 · 80 lb bags $1,012.50

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	3.02 yd³	10%	3.33 yd³ / 2.544 m³	USD	$548.98	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	136.1 bags	10%	150 bags	USD	$1,012.50	Source Spec Material / Tool
60 lb pre-mix bags	181.5 bags	10%	200 bags	USD	$1,080.00	Source Spec Material / Tool
#4 rebar sticks, 20 ft	20 sticks	10%	22 sticks / 20 × 6 m	USD	$308.00	Source Spec Material / Tool
Rebar chairs	100 crossings	10%	110 chairs	USD	$30.80	Source Spec Material / Tool
Tie wire rolls	100 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

$673.98

0.33 nominal 10 yd³ loads · 1 to order

80 lb bags

$1,012.50

60 lb alternative $1,080.00 · delivery weight 13,475 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	2.66	2.035	120	308	$564.19	$810.00
5 in	3.33	2.544	150	308	$673.98	$1,012.50
6 in	3.99	3.053	180	308	$783.78	$1,215.00

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: 14 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 is designed for a residential slab measuring 14 ft by 14 ft with a thickness of 5 inches. It incorporates #4 rebar spaced at 18 inches on center, adhering to the guidelines set forth in IRC R506.

Please note that soil design considerations are excluded from this calculation. It is essential to consult a qualified professional for soil analysis to ensure proper support for your slab.

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 preventing cracking.
Why is soil design excluded from this calculation?: Soil design is excluded because it requires specific analysis based on site conditions, which should be conducted by a qualified geotechnical engineer.
What is the significance of following IRC R506?: Following IRC R506 ensures that your slab design meets the minimum safety and performance standards for residential construction.