— Rebar & Reinforcement
Standard Bar Sizes (ASTM A615)
Bar number = nominal diameter in 1/8-inch units (e.g. a #8 bar is 8/8 = 1.000 in nominal diameter). #14 and #18 bars are not simple multiples of 1/8 in and are typically used only in columns.
| Bar No. | Diameter (in) | Diameter (mm) | Area (in²) | Area (mm²) | Weight (lb/ft) |
|---|---|---|---|---|---|
| #3 | 0.375 | 9.5 | 0.11 | 71 | 0.376 |
| #4 | 0.500 | 12.7 | 0.20 | 129 | 0.668 |
| #5 | 0.625 | 15.9 | 0.31 | 200 | 1.043 |
| #6 | 0.750 | 19.1 | 0.44 | 284 | 1.502 |
| #7 | 0.875 | 22.2 | 0.60 | 387 | 2.044 |
| #8 | 1.000 | 25.4 | 0.79 | 510 | 2.670 |
| #9 | 1.128 | 28.7 | 1.00 | 645 | 3.400 |
| #10 | 1.270 | 32.3 | 1.27 | 819 | 4.303 |
| #11 | 1.410 | 35.8 | 1.56 | 1006 | 5.313 |
| #14 | 1.693 | 43.0 | 2.25 | 1452 | 7.650 |
| #18 | 2.257 | 57.3 | 4.00 | 2581 | 13.600 |
Grade / Yield Strength
| Grade | Min. Yield (ksi) | Min. Tensile (ksi) | Typical Use |
|---|---|---|---|
| Grade 40 | 40 | 60 | Light residential slabs/footings, stirrups — increasingly uncommon |
| Grade 60 | 60 | 90 | Default grade for most structural/commercial reinforced concrete |
| Grade 75 | 75 | 100 | Heavy structural members, high-rise columns |
| Grade 80 | 80 | 105 | High-strength applications, congested reinforcement |
| A706 Grade 60/80 | 60 / 80 | 80 / 100 | Low-alloy, controlled chemistry — required where bars are welded or in seismic detailing |
Minimum Concrete Cover (ACI 318)
| Exposure Condition | Bar Size | Min. Cover |
|---|---|---|
| Cast against and permanently exposed to earth | All sizes | 3 in |
| Exposed to weather or in contact with earth | #6–#18 | 2 in |
| Exposed to weather or in contact with earth | #5 and smaller | 1½ in |
| Not exposed to weather/earth — slabs, walls, joists | #14, #18 | 1½ in |
| Not exposed to weather/earth — slabs, walls, joists | #11 and smaller | ¾ in |
| Not exposed to weather/earth — beams, columns (primary reinforcement, ties, stirrups) | All sizes | 1½ in |
Cover is measured from the concrete surface to the outermost surface of the steel (including stirrups/ties, if they're the outermost bar).
Standard Hook Minimum Bend Diameter (ACI 318)
| Bar Size | Primary Reinforcement (90°/180° hooks) | Stirrup/Tie Hooks |
|---|---|---|
| #3 – #5 | 6db | 4db |
| #6 – #8 | 6db | 6db |
| #9 – #11 | 8db | — (not permitted as stirrup/tie material) |
| #14, #18 | 10db | — |
db = nominal bar diameter. Bend diameter is measured to the inside of the bar.