Metric and US Bar Equivalents
| US bar | Diameter | Area | Soft metric | Nearest metric bar |
|---|---|---|---|---|
| #3 | 9.5 mm (0.375 in) | 71 mm² | No. 10 | 10 mm (79 mm²) |
| #4 | 12.7 mm (0.500 in) | 129 mm² | No. 13 | 12 mm (113 mm²) |
| #5 | 15.9 mm (0.625 in) | 198 mm² | No. 16 | 16 mm (201 mm²) |
| #6 | 19.1 mm (0.750 in) | 285 mm² | No. 19 | 20 mm (314 mm²) |
| #7 | 22.2 mm (0.875 in) | 388 mm² | No. 22 | 22 mm (380 mm²) |
| #8 | 25.4 mm (1.000 in) | 507 mm² | No. 25 | 25 mm (491 mm²) |
| #9 | 28.7 mm (1.128 in) | 645 mm² | No. 29 | 28 mm (616 mm²) |
| #10 | 32.3 mm (1.270 in) | 817 mm² | No. 32 | 32 mm (804 mm²) |
| #11 | 35.8 mm (1.410 in) | 1,006 mm² | No. 36 | 36 mm (1,018 mm²) |
How It Works
The calculator takes the nominal diameter of the bar you pick, works out its cross-section area and weight (7,850 kg/m³), and finds the bar in the other system with the closest area: the property that sets a bar’s strength.
Worked Example
A drawing from the US calls for #5 bars, and the local supplier stocks metric bars.
- A #5 bar is 5/8 in in diameter: 0.625 in, or 15.9 mm.
- Its area is π/4 × 15.9² = 197.9 mm², about 198 mm² (0.307 in²).
- The metric bar with the closest area is 16 mm: π/4 × 16² = 201 mm², 1.6% more.
- The 16 mm bar weighs 1.578 kg/m against 1.552 kg/m for the #5, so the tonnage hardly changes.
So a 16 mm bar is the nearest match, with slightly more steel. Always have the engineer confirm a bar substitution before ordering.