A call forwarding system forwards telephone calls based on presence information of a user as reported by computing devices associated with a telephone number. When a telephone system receives an incoming call directed to one of the telephone numbers of the user's computing devices, it sends an incoming call event to each computing device. Upon receiving the incoming call event from a telephone system, each computing device determines whether the user is most likely present at that computing device based on the presence information. When a computing device determines that the user is most likely present at that computing device, it sends a notification to the telephone system to forward the incoming call to the telephone number associated with that computing device to effect the automatic forwarding of a call based on presence information.