From The Washington Examiner:

There are no official statistics on how many guns Americans own, but the Small Arms Survey is the most widely recognized estimate of civilian, police, and military gun ownership in the world. Its most recent estimate puts civilian-owned firearms in America at about 400 million. That’s far more than in any other country in the world. There are more guns here than there are people. Civilians own 100 times as many guns as the military. Americans own so many guns it amounts to three times all the world’s militaries combined.