To work out how many years your savings will last when you are retired, you must calculate a value for each of four variables, these being P (the size of your savings), E, your outgoings each month, I, your income each month, and R, the annual interest rate. In the formula below, R should be expressed as a decimal, e.g., 5% = 0.05.

If you’d like, you can factor the effects of inflation into the calculations. First enter your current age, the age at which you wish to retire, and the amount you would like to withdraw each month. Then enter an interest rate you expect to earn on your investment, as well as the number of years you would like to make withdrawals.