The span of steel deck joists depends on several factors, including the type of joist, the load it needs to support (live load and dead load), the joist size, and the spacing between joists. Here are some general guidelines:

1. Light Gauge Steel Joists (commonly used in residential or light commercial construction):
   • Span can typically range from 10 to 30 feet depending on joist size, spacing, and load conditions.
2. Open Web Steel Joists (used in larger commercial and industrial projects):
   • Short-span joists can cover up to 60 feet.
   • Long-span joists (K-series or LH-series) can span 60 to 144 feet or more, depending on the specific application.
3. Heavy Load Requirements (commercial or industrial):
   • If the steel deck needs to support significant loads (e.g., mechanical equipment or heavy foot traffic), the joist spacing may be reduced, or larger joists may be needed, leading to a reduced span range.

Consulting with a structural engineer and referring to steel joist and deck manufacturers' load span tables is essential for precise measurements based on your project’s needs.