To call a U.K. phone number, dial 011 + 44 followed by the phone number. Calls to U.K. land lines also require an area code; this is inserted as 011 + 44 + area code + phone number. HowToCallAbroad.com provides a full list of U.K. area codes.
U.K. cellphone numbers are 10 digits long, but you must omit the beginning zero when dialing from the United States.
As of 2015, Skype also allows cheap calls to international phone numbers and is available on computers, most tablets and smartphones. To download Skype, click on the Downloads tab on Skype.com and select your device.