How long does it take to double your money in an FD at 7%?
At 7% annual interest compounded quarterly (typical for an FD), it takes about 9.99 years to double your money.
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).