How long does it take to make your money 4 times at 9%?
Based on these numbers, it takes about 16.09 years to reach that multiple.
How is this calculated?
This uses the compound interest formula solved for time: years = ln(multiple) / (n × ln(1 + rate/n)), where n is the compounding frequency. At 12% annual compounding, for example, money roughly doubles in about 6 years, following the well-known "Rule of 72" approximation (72 ÷ rate).