To call London from the USA, dial the international line, United Kingdom country code, London area code, and finally the telephone number of the person you are calling. This information applies to all USA phone numbers trying to reach a London number, even if you are dialing from within the area.
- Dial the international line
Dial the code for calling outside the USA, which is "011."
- Dial the U.K. country code
London is in England, which is a part of the U.K. Therefore, dial the country code of the U.K., which is "44."
- Dial London area code
Dial the area code for London, which is "20." Some telephone directories list it as "020", but you only need to include the "0" if you dial out from within the U.K.
- Dial the phone number
Dial the telephone number of the person you are calling, it should be six or seven digits, use it as it is without any modification.