Structural reinforcement requires precise material specifications. Our Rebar Size Converter translates standard ASTM rebar numbers into their physical diameter, cross-sectional area, and weight per unit length. Whether you're working with Imperial #3-#18 or Metric 10M-55M bars, our tool provides the engineering data needed for load-bearing calculations and site logistics.
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Rebar Size Converter
Convert rebar size numbers to diameter and weight specifications (ASTM standards).
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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.
About Standard Rebar Size Calculator
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.
3
Save Your Output
Click the download or copy button to export your results to your device or clipboard.
Key Features
ASTM & Metric Standards
Full support for US standard rebar numbers and Canadian/European metric sizes.
Weight Estimator
Calculates weight in lb/ft and kg/m to help with transportation and structural planning.
Area Calculations
Provides cross-sectional area (sq in, sq mm) for concrete reinforcement planning.
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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