Rebar Size Chart
Nominal diameter, cross-section area, and weight for every standard US bar size, #3 through #18, with the metric equivalents. Values are the ASTM A615 / A706 nominal dimensions.
| Size | Soft metric | Diameter (in) | Diameter (mm) | Area (in²) | Weight (lb/ft) | Mass (kg/m) |
|---|---|---|---|---|---|---|
| #3 | #10 | 0.375 | 9.5 | 0.11 | 0.376 | 0.560 |
| #4 | #13 | 0.500 | 12.7 | 0.20 | 0.668 | 0.994 |
| #5 | #16 | 0.625 | 15.9 | 0.31 | 1.043 | 1.552 |
| #6 | #19 | 0.750 | 19.1 | 0.44 | 1.502 | 2.235 |
| #7 | #22 | 0.875 | 22.2 | 0.60 | 2.044 | 3.042 |
| #8 | #25 | 1.000 | 25.4 | 0.79 | 2.670 | 3.973 |
| #9 | #29 | 1.128 | 28.7 | 1.00 | 3.400 | 5.060 |
| #10 | #32 | 1.270 | 32.3 | 1.27 | 4.303 | 6.404 |
| #11 | #36 | 1.410 | 35.8 | 1.56 | 5.313 | 7.907 |
| #14 | #43 | 1.693 | 43.0 | 2.25 | 7.650 | 11.38 |
| #18 | #57 | 2.257 | 57.3 | 4.00 | 13.60 | 20.24 |
Weight for a length of bar is length × weight per foot: a 20′ #5 is 20 × 1.043 = 20.9 lb. Multiply by the bar count for a bundle.
How to read a rebar size
The bar number is the nominal diameter in eighths of an inch. A #4 bar is 4⁄8 = ½″, a #5 is ⅝″, a #8 is a full inch. That rule holds through #8. The larger sizes are round bars with the same cross-section as the old square bars they replaced — #9, #10 and #11 match 1″, 1⅛″ and 1¼″ squares, #14 and #18 match 1½″ and 2″ squares — so their diameters are not clean eighths.
Every dimension here is nominal: the plain round bar that would weigh the same per foot. A real deformed bar measures slightly larger across its ribs. Weight and area are tied together by definition — nominal area is nominal weight divided by 3.40 lb/ft per square inch — which is why the areas in the table are rounded the way they are.
Soft-metric names
Since 1997, ASTM A615 bars have also carried a metric designation: the nominal diameter in millimetres, rounded. A #4 is a #13, a #5 is a #16. It is the same bar from the same mill — only the name changes. A drawing that calls for #13 bars wants #4s.
Canadian metric sizes
Canadian bars (CSA G30.18) are a genuinely different series, sized by cross-section area rather than diameter: 10M is 100 mm², 15M is 200 mm², and so on. 15M is close to a #5 but is not the same bar.
| Size | Diameter (mm) | Area (mm²) | Mass (kg/m) | Weight (lb/ft) | Nearest US size |
|---|---|---|---|---|---|
| 10M | 11.3 | 100 | 0.785 | 0.527 | between #3 and #4 |
| 15M | 16.0 | 200 | 1.570 | 1.055 | #5 |
| 20M | 19.5 | 300 | 2.355 | 1.583 | #6 |
| 25M | 25.2 | 500 | 3.925 | 2.638 | #8 |
| 30M | 29.9 | 700 | 5.495 | 3.692 | #9 |
| 35M | 35.7 | 1000 | 7.850 | 5.275 | #11 |
Which sizes show up where
#3 and #4 are the slab-on-grade sizes — driveways, patios, garage and shop floors, usually on 12″ to 18″ centres. #5 turns up in thicker slabs, footings, and foundation walls. #6 through #8 are beam, column, and structural-footing sizes. #9 and up are heavy structural bars that rarely move without a crane. The drawings govern; this is just what is usually on the truck.