Three million dollars sounds like a lot of money.And for the 22% of Americans who say they have less than $5,000 set aside for retirement, saving that much may seem like an impossible goal to work toward.But what if you could retire with $3 million by the time you were 67? The good news is that it is possible with persistent monthly saving, regardless of your age when you start saving.Personal finance site NerdWallet crunched the numbers, broken down by age group, to demonstrate how much you’ll need to stash away every month.First, let’s go over how they got there. The math assumes you are starting with no money in savings, that your investments will earn 6% annually and that you retire at age 67.You will need to take advantage of tools like your employer’s 401(k), which is a tax-advantaged retirement savings account, or a Roth individual retirement account or traditional IRA. Investment options include low-cost index funds.Now let’s dive into the figures. This video takes a look at how to make it happen.More from Invest in You:Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.