Rebar Calculator
Calculates rebar quantity, spacing, and cost for concrete reinforcement
Length of the concrete slab in feet
Width of the concrete slab in feet
Center-to-center spacing between rebar
Rebar diameter size
Enter all values to calculate rebar needs
Number of bars running across the width
Total number of rebar pieces
Total length of rebar needed
Approximate material cost
Frequently Asked Questions
What spacing should rebar be in a concrete slab?
Standard residential slabs use 16 or 18 inch spacing in a grid pattern. Driveways and garage floors often use 12-inch spacing for extra strength. The specific spacing depends on the slab thickness, load requirements, and local building codes.
What size rebar do I need?
Number 3 (3/8-inch) rebar is common for residential patios and sidewalks. Number 4 (1/2-inch) is standard for driveways and garage floors. Number 5 (5/8-inch) is used for foundations, retaining walls, and commercial applications requiring more tensile strength.
How far should rebar be from the edge of concrete?
Rebar should have a minimum of 3 inches of concrete cover on all sides for ground-contact applications. For slabs not in contact with ground, 1.5 inches is typical. Proper cover protects the rebar from moisture and corrosion.
Do I need rebar in a 4-inch slab?
A 4-inch residential patio slab can often use welded wire mesh instead of rebar. However, rebar is recommended for driveways, areas with heavy loads, or expansive soils. If the slab will carry significant weight or span over soft soil, rebar is the safer choice.
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