Rebar Sizes (ASTM and Metric)
ASTM A615 US bar numbers #3 to #18 and common metric sizes with diameter, area and mass.
Reinforcing bar (rebar) is the steel that carries tension in concrete. In the US it is sold by bar number, which is the nominal diameter in eighths of an inch: a #5 bar is 5/8 inch. Metric bar is sold by diameter in millimeters. This table lists the nominal diameter, cross-section area and mass per meter of each size.
The table
| Bar size | Nominal diameter (mm) | Nominal diameter (in) | Area (mm2) | Mass (kg/m) | Mass (lb/ft) |
|---|---|---|---|---|---|
| US #3 | 9.5 | 0.375 | 71 | 0.559 | 0.376 |
| US #4 | 12.7 | 0.5 | 127 | 0.994 | 0.668 |
| US #5 | 15.9 | 0.625 | 198 | 1.554 | 1.044 |
| US #6 | 19.1 | 0.75 | 285 | 2.237 | 1.503 |
| US #7 | 22.2 | 0.875 | 388 | 3.045 | 2.046 |
| US #8 | 25.4 | 1 | 507 | 3.978 | 2.673 |
| US #9 | 28.7 | 1.128 | 645 | 5.061 | 3.401 |
| US #10 | 32.3 | 1.27 | 817 | 6.416 | 4.311 |
| US #11 | 35.8 | 1.41 | 1007 | 7.908 | 5.314 |
| US #14 | 43 | 1.693 | 1452 | 11.401 | 7.661 |
| US #18 | 57.3 | 2.257 | 2581 | 20.262 | 13.616 |
| Metric 6 mm | 6 | 0.236 | 28 | 0.222 | 0.149 |
| Metric 8 mm | 8 | 0.315 | 50 | 0.395 | 0.265 |
| Metric 10 mm | 10 | 0.394 | 79 | 0.617 | 0.414 |
| Metric 12 mm | 12 | 0.472 | 113 | 0.888 | 0.597 |
| Metric 16 mm | 16 | 0.63 | 201 | 1.578 | 1.061 |
| Metric 20 mm | 20 | 0.787 | 314 | 2.466 | 1.657 |
| Metric 25 mm | 25 | 0.984 | 491 | 3.853 | 2.589 |
| Metric 32 mm | 32 | 1.26 | 804 | 6.313 | 4.242 |
| Metric 40 mm | 40 | 1.575 | 1257 | 9.865 | 6.629 |
Source and notes: ASTM A615 / A615M reinforcing bar sizes (US numbers are eighths of an inch: #8 is 8/8 = 1 inch; #9, #10, #11, #14 and #18 have the diameter of the old square bars of equal area) and common metric sizes. Area and mass are computed from the nominal diameter at 7 850 kg/m3.
How to use this table
- Find the bar size.
- Use the area for the steel in a section and the mass for ordering by weight.
- To convert a number to a diameter in inches, divide it by 8 (up to #8).
Worked example
- A #8 bar has an area of 507 mm². A #4 bar has 127 mm², so it takes 4.0 #4 bars to replace one #8.
- A 12 m #5 bar weighs 18.6 kg (41.1 lb).
Notes and cautions
- Bars #9 and above have the diameter of the old 1, 1-1/8, 1-1/4 inch square bars that had the same area; the number is no longer exactly an eighth of an inch.
- Grades (Grade 40, 60, 75 and 80 in ksi yield) are a separate choice. Grade 60 (420 MPa) is the most common.
- Deformations (the ribs) make the real mass slightly different from the plain round bar figures.
Related tools and guides
FAQ
What is a #4 rebar?
A deformed bar of 1/2 inch (12.7 mm) nominal diameter, 127 mm² in area, weighing 0.994 kg/m.
What metric bar equals #5?
About 16 mm; #5 is 15.9 mm. Metric 12 mm is close to #4 (12.7 mm).
Sources
- ASTM A615 / A615M (deformed and plain carbon steel bars for concrete reinforcement). Area and mass computed from the nominal diameter at 7 850 kg/m³.
- ASTM A615 / A615M reinforcing bar sizes (US numbers are eighths of an inch: #8 is 8/8 = 1 inch; #9, #10, #11, #14 and #18 have the diameter of the old square bars of equal area) and common metric sizes. Area and mass are computed from the nominal diameter at 7 850 kg/m3.