How much money do you need to save for retirement?

Exactly how much money will you need to retire comfortably?

The majority of Americans think they will need less than $1 million, according to the Merrill Edge Report Fall 2016. But 19 percent have no idea how much they will need.

The breakdown:

9 percent think they will need more than $2 million

14 percent believe they will need $1 million to $2 million

24 percent say $500,000 to $1 million

23 percent say $100,000 to $500,000

9 percent say $0 to $100,000

And 19 percent say they just don't know

Even with many Americans underestimating their "magic number," Merrill says, 40 percent of retirees said their estimates would be difficult to reach or are "virtually unattainable."

"In order to reach their retirement goals, nearly one in five (17 percent) respondents are relying on luck, saying they would need to win the lottery," according to the report.

The truth is, and many financial planners will tell you, there is no "magic number." How much you need to save for retirement will depend on how much you spend. Even someone who saves $2 million will run out of money in retirement if they overspend and don't adhere to a budget. And someone who has only $500,000 might live comfortably if they have a lifestyle that does not require much cash.