The IndiaFirst Life pension planner calculates how much of a retirement corpus you will require to comfortably live your retired life. To do this, the retirement calculator needs to factor in how long the corpus has to last you. Suppose you retire at the age of 60 and estimate life expectancy up to the age of 85. In that case, the IndiaFirst Life retirement calculator has to calculate how much corpus you would require to manage those 25 years after retirement.