There are many "calculators" in the Internet that you can use for free to estimate how much you would need to sustain your specific annual expense in retirement and for how many years.

Most of them tended to be designed for the US market where they included provision for social security when a person reaches a certain age.

I think the simplest and most relevant retirement calculator is the one from our own POSB. You can try it out with this link : internet-banking.dbs.com.sg/IB/Welcome
(You need to add s:// to the above to get to the website)

Using the POSB retirement calculator, it showed that I could retire now (at 56) with a monthly expense of $10,800 (or $129.6k pa), sustain this retirement expense for 30 years, till 86! and still have $1m left over. This calculation considered a 3% inflation rate.

As inputs for the calculation, they needed only the following:
1. Current investment holdings
2. Current CPF savings
3. Cash holdings (including FDs)
4. Current salary and how much of it (eg 70%) you will need in retirement
5. Your current age, when you want to retire and how long in retirement

It is good to know that I could retire now if I wanted to, and maintain my current lifestyle. $10,800 pm should enable us to continue owning a car, have house help, attend live concerts at MBS, and travel once a year.

But we will try and work till the official retirement age of 62 and still enjoy the above activities in the meantime.