The required minimum distribution from a traditional IRA is calculated annually. It is based on the value of the account at the end of the preceding year and the recipient's age at the end of the current year, according to Kiplinger.
Online calculators are available through sites such as Kiplinger and Bankrate. These calculators are not accurate if the sole beneficiary is a spouse more than 10 years younger than the account owner, Kiplinger warns. In that situation, the worksheets on the Internal Revenue Service website, used with tables from IRS Publication 590, provide a more accurate RMD.
Taxpayers can take more than the required minimum, the IRS notes, but must include the distribution in their taxable income to the extent it was not previously taxed.