Rebar Calculator

How much rebar for a concrete slab or wall?

LINEAR FEET
LF
of rebar

Usage Tip

#4 rebar (1/2 in) is standard for slabs. Splice or overlap at least 12 inches where bars join.

THE MATH
Grid LF × (1 + overlap %)
Where: bars = spaces + 1 in each direction
• #4 rebar weighs 0.668 lb/ft
• Splice/overlap at least 12 in where bars join
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.