<prompt> Human: Im 23 and am trying to project my future. Have most of my money in low cost market funds. Do compound interest calculators, but they fluctuate wildly based on the . I never know what to put in. Everyone is so sketchy about it from what it seems as past results do not guarantee future returns, but surely everyone has a base number they are working from?  <response>: You can use something like cFIREsim to plan your future investingretirement. It uses historical data to give estimates of how your savingsinvestments would fare over time. This can give an idea of average return, while taking into account the timing of recessions and booms. - This is an example I made for you. Assuming: Work for 30 years retirement is set at 2044 Portfolio starts at 0 Basic 7525 stockbond allocation, with fairly low fees You invest 10,000yr, and increase that amount with inflation. Out of 113 different 30-year periods that it looked at, your average portfolio for retirement would be 817,925.25 in todays dollars.You can flip this around, start a new simulation, and tell it your spending to see if it would last in retirement as you withdraw it. You can also add it all sorts of other details estimated SS, any pensions you might get, extra savings, one-time or recurring spending events in the future, etc. I highly recommend reading the tutorial and blog posts. Pretty high learning curve, and lots of options... it can make anyones mind spin. 