Investing about $300 per month can make you a millionaire if you begin in your 20s.
If you start later or want even more money for retirement, you'll have to get serious. How much you'll need to invest every month will depend on how old you are when you start and how much money you want for retirement.
CNBC crunched the numbers, broken down by age group, to show how much you'll have to stash away every month.
Check out this video to see how you can make it happen.
Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.