Trying to figure out whether you can afford to retire is like putting together pieces of a financial jigsaw puzzle. First, you need to estimate how much you'll spend in retirement. Then you must consider the income you'll collect in retirement from pensions and Social Security - as well as the amount you can afford to draw from your personal savings or other sources.
The idea is to assemble the various pieces, and then see whether the picture of retirement life that emerges is acceptable to you.
To help bring the retirement picture into better focus, try plugging all your pertinent financial information - including pensions, Social Security, retirement investment accounts and anticipated retirement expenses - into an online calculator. The calculator can crunch all the numbers and assess your odds of being able to retire on the schedule you envision.
Revisit the calculator and all the different pieces of the puzzle each year, in order to make sure you remain on track. 
