Compound interest calculator
Enter your starting amount, how much you add each month, the yearly return and the time frame.
You'd have$638,288
What you put in$250,000
What your money earned$388,288
What you put in What your money earned
How it's calculated
Each month your contribution is added and the money grows at the monthly rate (the yearly rate divided by 12). What you earn is reinvested and starts earning too: that's compound interest.
The rule of 72 gives a quick idea: divide 72 by the yearly return to get how many years it takes your money to double (at 8%, about 9 years).
It's a calculation with a fixed return, to show the idea. In reality returns go up and down and aren't guaranteed. For goals under 3 years, think about fixed income (such as CETES).