I have a client who only has around 300k in all of her retirement and savings accounts... Less than ideal right? Well she lives on her 1100.00 a month SSI.
I also have a client who has well over 3 million in total retirement savings and also has a $22,000.00 a month pension (former HP exec). He spends all of his pension income each month and still draws down well above 4% of his asset value each year which is higher than what we recommend.
Point is, analyze what you'll need each month to live on... From there times that by 12 and then use age 94 or so for your life expectancy. Multiply your annual income need with your life expectancy from retirement to death and there you have it.
Also, keep 6 months worth of living expenses in cash for emergencies. All of the above is a decent starting point into your retirement planning.