Why There's No One Standard for Measuring Rebar Sizes in the U.S.
For the many of us who rely on Google to convert from inches to meters, making sense of the various systems of measurement for classifying rebar sizes can be a daunting task.
Before referring to commonly used rebar size conversion tables, it's first important to understand why standards have been so hard to come by. Both imperial (inch-pound) and metric measurement systems are currently used in the U.S. construction industry. While virtually all federal construction is now designed and built adhering to the metric system, only around one-third of U.S. states have made the leap to metric.
Rebar Sizes in the U.S.
In the U.S., imperial bar designations represent the bar diameter in fractions of ? inch, whereas metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm. For the sake of simplicity, and your sanity, we'll save European metric bar designations for another discussion.
In 1997, a large number of U.S. steel mills spearheaded a new way of designating rebar sizes. Known as soft metric, this method enables the construction industry to provide the same reinforcing bars to both inch-pound and metric construction projects. High-quality rebar is always in stock and available from professional suppliers like White Cap.
Size is one of a series of individual markings that is applied as part of the manufacturing process for each individual reinforcing bar. Others include markings for the producing mill, manufacturing material and grade.
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Imperial sizes
Imperial bar appellations represent rebar stick
diameters in fractions of an inch, such that #8 =
8/8 inch = 1 inch diameter.
| Imperial
Bar Size |
"Soft"
Metric Size |
Weight
(lb/ft) |
Nominal Diameter
(in) |
Nominal Diameter
(mm) |
Nominal Area
(in2) |
| #3 |
#10 |
0.376 |
0.375 |
9.525 |
0.11 |
| #4 |
#13 |
0.668 |
0.500 |
12.7 |
0.20 |
| #5 |
#16 |
1.043 |
0.625 |
15.875 |
0.31 |
| #6 |
#19 |
1.502 |
0.750 |
19.05 |
0.44 |
| #7 |
#22 |
2.044 |
0.875 |
22.225 |
0.60 |
| #8 |
#25 |
2.670 |
1.000 |
25.4 |
0.79 |
| #9 |
#29 |
3.400 |
1.128 |
28.65 |
1.00 |
| #10 |
#32 |
4.303 |
1.270 |
32.26 |
1.27 |
| #11 |
#36 |
5.313 |
1.410 |
35.81 |
1.56 |
| #14 |
#43 |
7.650 |
1.693 |
43 |
2.25 |
| #18 |
#57 |
13.60 |
2.257 |
57.33 |
4.00 |
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Metric sizes
Metric bar designation represents the specified
rebar stick diameter in millimeters, rounded to the
nearest 5 mm.
| Metric
Bar Size |
Mass
(kg/m) |
Nominal Diameter
(mm) |
Cross-Sectional
Area (mm2) |
| #10 M |
0.785 |
11.3 |
100 |
| #15 M |
1.570 |
16.0 |
200 |
| #20 M |
2.355 |
19.5 |
300 |
| #25 M |
3.925 |
25.2 |
500 |
| #30 M |
5.495 |
29.9 |
700 |
| #35 M |
7.850 |
35.7 |
1000 |
| #45 M |
11.775 |
43.7 |
1500 |
| #55 M |
19.625 |
56.4 |
2500 | |
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