How much rebar do I need for a 24x24 slab?

Construction & MaterialsACI 318 Structural Standards

Concrete Rebar Grid & Spacing Calculator

Calculate total rebar sticks, grid layout, 30-diameter lap splice waste, and total steel weight for reinforced concrete slabs.

Construction & Materials Field StandardsACI 318 Structural Standards

Engineering formulations calibrated to IPC, UPC & NEC specificationsSub-Zero Cold Climate Tolerances

Quick Summary & Key Answer

For a 20' × 30' concrete slab with standard #4 (1/2") rebar placed at 18-inch on-center grid spacing, you need approximately 770 linear feet of rebar (thirty-nine 20-foot sticks) weighing 514 lbs including 10% lap splice allowance.

#4 rebar (1/2" diameter) is the standard for 4-inch residential concrete slabs.
Rebar must be suspended in the middle to upper third of the slab depth using rebar chairs.
Lap splices require a minimum 30 bar diameter overlap (15 inches for #4 bar).

Interactive Calculator

Adjust inputs for real-time results

Slab Lengthfeet

feet

Slab Widthfeet

feet

Grid Spacing

Rebar Size

Calculated OutputACI Grid Sized

Standard 20-Foot Rebar Sticks

47 Sticks

Total Linear Footage (with 10% lap): 924 ft
Total Steel Weight: 617 lbs
Steel Weight in US Tons: 0.31 tons
Grid Intersection Tie Points: 294 ties

Note: Based on 30-bar-diameter lap splice minimum per ACI 318. Maintain 2 inches of concrete edge clearance.

ACI 318 Placement Standards

Never let rebar rest on the gravel sub-base during the concrete pour; lift bars with plastic dobies or rebar chairs.

Frequently Asked Questions

Common questions regarding this calculation and code compliance

A 24'x24' slab with 18" grid spacing requires approximately 38 twenty-foot sticks of #4 rebar.