How thick is 18 gauge steel?

Depends on what kind of steel: 18 Gauge Standard Steel is .0478 Inches. 18 Gauge Galvanized Steel is: 0.0516 inches thick.

FYI 18 Gauge Aluminum is 0.0403

18 gage steel is 0.0478 inches thick 18 gage steel is 0.0478 inches thick