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Rebar Size Converter

Convert rebar size numbers to diameter and weight specifications (ASTM standards).

Standard Rebar Specs

Rebar sizes are based on eighths of an inch. For example, #4 rebar has a diameter of 4/8" (0.500").

Nominal Dia (in)0.500
Nominal Dia (mm)12.7
Weight (lb/ft)0.668
Weight (kg/m)0.994

ASTM Standards

These sizes follow standard US ASTM A615/A615M specifications for deformed and plain carbon-steel bars for concrete reinforcement.

Construction Note

Size numbers from #9 to #18 use a slightly different diameter calculation to match the cross-sectional area of square bars previously used in construction.

Standard Rebar Size Calculator

Convert rebar size numbers to diameter, area, and weight per unit length (Imperial and Metric).

1

Select Number

Choose your rebar size (e.g., #4, #5).

2

Check Specs

View diameter in inches/mm and weight in lb/ft or kg/m.

Frequently Asked Questions

It is 1/2 inch in diameter (4/8 of an inch). The number represents eighths of an inch.

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