The New York Times has an interesting “Comeback Calculator” to visualize when a portfolio could return to peak levels. Assume you had a portfolio that was worth $100,000 at the start of 2008 and it is now worth only $70,000. If you didn’t add new money to the portfolio and the returns average 8% in future years, it would take 8 years for the portfolio to recover (in real terms). But, if you keep adding, say $2,000 to the portfolio every year, it will recover to the previous peak in 5 years. Of course, your actual experience is likely to be dramatically different, given that stock market returns are never going to weigh in at 8% year after year.

The Stingy Investor website features a far better calculator that uses actual past returns of various asset classes to compute returns for different asset allocation scenarios.