The compression ratio is the output pressure divided by the input pressure (in absolute pressures).

single stage oil injected screw compressors typically have an output pressure of 8 to 14 bar absolute (7 - 13 bar relative).

In which case the compression ratio is also in the range of 7 to 14.

Although higher pressure ratio's  can be achieved with oil-injected screw compressors (often in portable diesel compressors).

Hope this answers your questions :)

Thanks,

Cas