You need to have 25 times your annual expense at the time of retirement.
Your portfolio needs to make close to 10% pa at the time of retirement. To earn that rate of return, you need to have a reasonable mix of equity, debt and real estate at the time of retirement.
Of the 10% that your portfolio makes, you can use only 4% for your annual needs. The balance 6% needs to be invested back in the portfolio to maintain your income for future inflation protection.