As a rule of thumb, most financial advisors suggest that you save 10% to 15% of your salary.

And if your goal is to get to $750,000, the percentage you need to invest will vary drastically based on how old you are when you start.  

Here's a case study.

Starting to invest when you turn 25 means that saving 13% of your $35,000 income, more than $375 every month, will put you on track to retire with $750,000.

Check out this video to see a full breakdown for different timelines.

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Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.