The required minimum distribution is calculated by dividing the prior December 31st balance of an IRA by a life expectancy factor published in IRS tables, according to the IRS. Therefore, this amount is different for everyone. RMDs must be taken for the year in which a person turns 70 1/2.
According to Bankrate, a person must start taking out IRA money in specific increments by April 1st following the year he reaches 70 1/2 years of age. The Uniform Lifetime Table is the most commonly used life-expectancy chart to calculate RMDs. The IRS website provides the three tables that are used.