What is the designation for a #5 rebar in terms of diameter?
Correct Answer
B) 5/8 inch
Rebar sizes are designated by numbers that represent eighths of an inch. A #5 rebar has a diameter of 5/8 inch (5 × 1/8 = 5/8). This is the standard system used in the United States for identifying reinforcing steel sizes.
Why This Is the Correct Answer
The US rebar designation system uses numbers that represent eighths of an inch in diameter. A #5 rebar means 5 eighths of an inch, which equals 5/8 inch diameter. This standardized system allows contractors and engineers to quickly identify rebar sizes without confusion. The number directly correlates to the fractional diameter measurement in eighths.
Why the Other Options Are Wrong
Option A: 0.5 inch
1/2 inch would be the diameter of a #4 rebar (4/8 = 1/2). This is one size smaller than #5 rebar and is commonly confused because 1/2 inch is a familiar fraction that people might associate with the number 5.
Option D: 5/16 inch
5/16 inch is not a standard rebar size in the US system. This fraction doesn't follow the eighths-based designation system and would fall between #2 (2/8 = 1/4 inch) and #3 (3/8 inch) rebar sizes.
Memory Technique
Think 'Rebar Eighths Rule' - the number IS the numerator over 8. #3 = 3/8, #4 = 4/8, #5 = 5/8, #6 = 6/8, etc. The rebar number tells you how many eighths!
Reference Hint
ACI 318 Building Code Requirements for Structural Concrete, Chapter 20 (Steel Reinforcement) or construction materials reference sections covering reinforcing steel specifications
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