What is the code to ring California from Ireland?

The code to call California in the United States from Ireland using landlines is 001 (international access code for the United States) followed by the area code of the specific city in California you are calling. Alternatively, you can use a mobile phone and dial +1 (country code for the United States) followed by the area code.

It's important to note that some telecommunications providers may have additional charges or require special instructions for international calling, so it's always a good idea to confirm with your service provider before making the call.