#18 Rebar (2-1/4 Inch Jumbo Bar)
Authoritative dimensional properties, unit weight, cross-sectional area, spacing tables, standard hook geometries, and ACI 318-19 tension development length for structural concrete design.
| Bar Designation | #18 | Code Standard | ASTM A615 / A706 |
| Nominal Diameter (db) | 2.257 in | Metric Diameter | 57.33 mm |
| Cross-Sectional Area (Ab) | 4 in² | Metric Area | 2581 mm² |
| Linear Weight | 13.6 lb/ft | Metric Mass | 20.24 kg/m |
| Nominal Perimeter | 7.091 in | Metric Perimeter | 180.1 mm |
| Minimum Clear Spacing | max(1.0″, 2.257″) | ACI Provision | ACI 318-19 §25.2.1 |
| Hook Type | Min. Inside Bend Pin | Extension Length (US) | Extension Length (SI) |
|---|---|---|---|
| 90° Standard Hook | 22.6″ (573 mm) | 27.1″ (12db) | 688 mm |
| 180° Standard Hook | 22.6″ (573 mm) | 9″ (max(4db, 2.5″)) | 229 mm |
Common Structural Applications
- ›The largest standard reinforcing steel bar in ASTM specifications
- ›Supertall skyscraper mega-columns and core wall transfer foundations
- ›Major suspension bridge anchorages and nuclear containment domes
Lap splicing is strictly prohibited by code. Requires heavy mechanical couplers (such as grip or threaded sleeves) or field CAD-welding. Weighs 13.6 lb/ft (20.2 kg/m).
#18 Rebar Spacing Table (As / Unit Width)
Area of longitudinal reinforcement provided for slabs, walls, and footing mats at given on-center spacings.
| 3″ o.c. | 4″ o.c. | 5″ o.c. | 6″ o.c. | 7″ o.c. | 8″ o.c. | 9″ o.c. | 10″ o.c. | 12″ o.c. | 14″ o.c. | 16″ o.c. | 18″ o.c. |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 16.000in²/ft | 12.000in²/ft | 9.600in²/ft | 8.000in²/ft | 6.857in²/ft | 6.000in²/ft | 5.333in²/ft | 4.800in²/ft | 4.000in²/ft | 3.429in²/ft | 3.000in²/ft | 2.667in²/ft |
ACI 318-19 Tension Development Length (ld)
Calculated using ACI 318-19 Section 25.4.2.3 simplified method for Grade 60 (420 MPa) deformed bars in normal-weight concrete with clear spacing ≥ db and clear cover ≥ db.
| Concrete Strength (f'c) | Bottom Bars (ld) [ψt = 1.0] | Top Bars (ld) [ψt = 1.3] | Governing Provision | Minimum Limit |
|---|---|---|---|---|
| 3,000 psi | 123.6″(3139 mm) | 160.7″(4082 mm) | ACI 318-19 Table 25.4.2.3 | ld ≥ 12″ (300 mm) |
| 4,000 psi | 107.1″(2720 mm) | 139.2″(3536 mm) | ACI 318-19 Table 25.4.2.3 | ld ≥ 12″ (300 mm) |
| 5,000 psi | 95.8″(2433 mm) | 124.5″(3162 mm) | ACI 318-19 Table 25.4.2.3 | ld ≥ 12″ (300 mm) |
| 6,000 psi | 87.4″(2220 mm) | 113.6″(2885 mm) | ACI 318-19 Table 25.4.2.3 | ld ≥ 12″ (300 mm) |
Design Reinforcement with #18 in AXIS
Run instant ACI 318-19 beam flexure, shear stirrup spacing, column P-M interaction, and development length checks with full KaTeX step-by-step audit logs.