An easy way to figure your return on investments is to use a simple “rule of 72” equation on the figure. Divide 72 by the interest rate will give you a very close forecast of how long (in years) it will take for your investment to double.
Ex.: I put $10,000 into a bond fund that is yielding 18% (they are out there), 72 divided by 18 equals 4.0. I will have $20,000 in four years. There is another formula that shows double and triples returns, but it involves square roots and not many people care for it.
Good Luck, invest in what makes since.