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 site-specific and requires a geotechnical analysis to determine the appropriate foundation design based on soil conditions.

What does IRC R506 cover?

IRC R506 provides guidelines for the design and construction of concrete slabs on grade, including requirements for reinforcement, thickness, and other structural considerations.

10 by 10 ft slab at 8 inches

Calculate the specifications for a 10 ft by 10 ft residential slab at 8 in thickness with #4 bars at 18 in spacing. Note: Soil design is excluded. Compliant with IRC R506.

Formula SSC-2026.1

Formula SSC-2026.1 · 4,000 PSI

Order volume

3.20 yd³

2.450 m³ placed+waste

Order weight

12,980 lb

5,888 kg

80 lb bags

145

4 pallets at 42 bags

60 lb bags

193

0.45 ft³ yield each

Rebar

220.00 ft

18 × 20 ft · 20 × 6 m · 162 lb

Ready-mix vs bags

$653.81

Truck $653.81 · 80 lb bags $978.75

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	2.91 yd³	10%	3.20 yd³ / 2.450 m³	USD	$528.81	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	131.1 bags	10%	145 bags	USD	$978.75	Source Spec Material / Tool
60 lb pre-mix bags	174.8 bags	10%	193 bags	USD	$1,042.20	Source Spec Material / Tool
#4 rebar sticks, 20 ft	18 sticks	10%	20 sticks / 20 × 6 m	USD	$280.00	Source Spec Material / Tool
Rebar chairs	49 crossings	10%	54 chairs	USD	$15.12	Source Spec Material / Tool
Tie wire rolls	49 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

$653.81

0.32 nominal 10 yd³ loads · 1 to order

80 lb bags

$978.75

60 lb alternative $1,042.20 · delivery weight 12,980 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	2.34	1.786	106	242	$510.41	$715.50
5 in	2.55	1.952	115	242	$546.26	$776.25
6 in	2.77	2.118	125	242	$582.11	$843.75

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: 10 by 10 ft slab at 8 inches

Prepared by

Date

Verified by (PE / electrician / inspector)

License number

Signature

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 slab measuring 10 ft by 10 ft with a thickness of 8 inches. The design incorporates #4 rebar spaced at 18 inches, ensuring structural integrity in compliance with IRC R506.

It is important to note that soil design considerations are excluded from this calculation. Always consult a licensed professional for comprehensive design and site-specific evaluations.

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 site-specific and requires a geotechnical analysis to determine the appropriate foundation design based on soil conditions.
What does IRC R506 cover?: IRC R506 provides guidelines for the design and construction of concrete slabs on grade, including requirements for reinforcement, thickness, and other structural considerations.