New Delhi, Sept. 10 -- Planning for retirement requires careful consideration of how quickly your savings can grow over time. This estimate can give you an idea of the retirement corpus you might need and help you make prudent financial decisions.

The 'Rule of 70' is a simple formula that helps investors estimate how long it will take for their investments to double. It also assumes a constant annual rate of return to ensure clear calculations.

There are several alternatives to the 'Rule of 70'; these are the 'Rule of 72' and the 'Rule of 69'. These are yet another way that can facilitate constructive retirement planning.

For example, if an investment earns about 7% annually, dividing 70 by 7 gives 10 years. This means that an investme...