Most car radios use a code tied to the VIN or a specific database (e.g., Bosch, Delphi, Mitsubishi). No universal “calculator” exists across brands. Many forums (like Reddit r/CarAV or Drive Accord) show that these sites are fake.
You must remove the radio or use a button combination (like pressing 1 and 6 simultaneously on Ford models) to find the serial number printed on the device’s label.
Elias’s experience highlights the pros and cons of using RadiocodesCalculator.com.