While minimum distributions from an IRA during retirement are required beginning at age 70.5, the amount of these required distributions depends on the value of the IRA and the life expectancy of the retiree, according to the Internal Revenue Service. However, Roth IRAs do not have required minimum distributions.
Bankrate provides a calculator to help retirees calculate the required minimum distributions from their IRA. The calculations require the total value of the IRA, the person's age at the end of the current year and the estimated rate of return. Other factors that may affect the amount of a required minimum distribution include whether the person's birthdate is in the second half of the year and the age of his beneficiary.