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What you need to save monthly to retire with $1 million to $3 million, broken down by age

How to retire with $1 million, $2 million or $3 million in savings

Americans need to save more for retirement.

And for the 15% of Americans who have no retirement savings at all, just getting started can seem overwhelming.

If you begin now, you can save $1 million, $2 million or $3 million with the right amount of time and dedication. How much you'll need to save every month will depend on how old you are when you start saving and how much money you want for retirement.

Personal finance site NerdWallet crunched the numbers, broken down by age group, to demonstrate how much you'll have to stash away every month.

First, let's go over how we got there. The math assumes you have  no money in savings, that your investments will earn 6% annually and that you retire at 67.

Now let's dive into the figures. This video takes a look at how to make it happen.

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Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.