THUMB RULES USED IN FINANCE:

Rule of 72:
This tells you in how much time your money will double.
Divide 72 by the interest rate you are compounding your money with and you will arrive at the number of years it will take to double in value.
Example:
If the interest rate is 9%, then your money will double in:
(72/9=8) 8 years

Rule of 114:
Use this to estimate how long it will take to triple your money.
It works the same way as the rule of 72.
Example:
Divide 114 by the interest rate to know in how many years Rs 10,000 will become Rs 30,000.

Rule of 44:
Similarly, this tells you in how much time your investment will quadruple in value.
Example:
If the interest rate is 12%, Rs 10,000 becomes Rs 40,000 in 12 years.

Rule of 70:
This is a useful rule for predicting your future buying power.
Divide 70 by the current inflation to know how fast the value of your investment will get reduced to half its present value.
This is especially useful for retirement planning, as it affects the way you set up your monthly withdrawals. However, do remember that inflation varies from time to time.
Example:
Inflation of 7% will reduce the value of your money to half in
(70/7 = 10) 10 years

Pay yourself first rule:
Right from your first salary, put away a little for your retirement.
Ideally 10% of your income should go into this.
It is important to increase the amount as your income rises over the years.

100 minus your age rule:
This rule is used for asset allocation into equity and debt.
Subtract your age from 100 to find out how much of your portfolio should be allocated to equities and balance remaining for debt investment.