Rebar Calculator
The Rebar Calculator estimates how much reinforcing bar you need for a simple perpendicular grid pattern in a concrete slab, based on your slab size and bar spacing.
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How This Tool Works
Enter your slab's length and width, your rebar grid spacing, and standard stick length to calculate total linear feet and sticks needed.
Formula & Method
Bars in each direction = (span in inches ÷ spacing) + 1. Total linear feet = (bars one way × length) + (bars the other way × width). Sticks = total linear feet ÷ stick length (usually 20 ft).
Example Calculation
A 10×10 ft slab with rebar on a 12 inch grid needs 11 bars each direction — about 220 linear feet, or 11 sticks of 20 ft rebar.
Frequently Asked Questions
What rebar spacing is standard for slabs?+
Residential slabs commonly use 12–18 inch grid spacing, while structural or high-load slabs may require tighter spacing per an engineer's specification.
Does this account for overlap between sticks?+
No, this gives the base linear footage needed. Add roughly 40 bar diameters of overlap at every splice as recommended by your local code or engineer.
Should a structural engineer review my rebar plan?+
For any load-bearing or structural slab, always have a qualified engineer specify rebar size, spacing, and placement — this tool is for general planning only.
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