Free Calculator Tool

Concrete Rebar Calculator

Estimate rebar reinforcement for concrete slabs, foundations, and walls. This rebar calculator for concrete computes total linear footage, bar count, and approximate weight using your slab dimensions and rebar spacing.

Rebar Grid Formula

Bars in each direction = (dimension / spacing) + 1, then multiply by perpendicular dimension for total length

How To Use This Tool

Enter slab or wall length and width in feet.
Set rebar spacing in inches (commonly 12 or 16).
Review total linear feet and weight estimate.

Calculate Rebar for Concrete Slabs

Enter slab dimensions and rebar spacing to estimate total rebar length and bar count.

Length (ft) Longest side of the slab Width (ft) Shortest side of the slab Rebar Spacing (in) 12 in on-center is common residential Bar Size

Ready to calculate?

Enter values and run the calculator to see detailed results.

Concrete Rebar Calculator FAQs

Clear answers for common estimation and planning questions.

What rebar spacing should I use for a concrete slab?

Common residential slab rebar spacing is 12 inches on center in both directions. Heavy-load slabs may use tighter spacing like 8 or 10 inches.

What size rebar is used for concrete slabs?

Number 3 and number 4 rebar are most common for residential slabs. Number 5 and 6 bars are used for heavier structural applications.

How do I calculate rebar weight?

Multiply total linear feet by the weight per foot for your bar size. For example, number 4 rebar weighs about 0.668 pounds per foot.

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