Generally, a required minimum distribution (RMD) is calculated for each account by dividing the prior December 31 balance of that IRA or retirement plan account by a life expectancy factor the IRS publishes in Publication 590, Individual Retirement Arrangements (IRAs). There are three separate tables:

The Uniform Lifetime Table (Table III) is used by an unmarried owner, a owner whose spouse is not the sole beneficiary, and an owner whose spouse is not more than 10 years younger;

The Joint and Last Survivor Table (Table II) is used by a married owner whose spouse is both more than 10 years younger and the sole beneficiary of the account; and

The Single Life Expectancy Table (Table I) is used by a beneficiary of an account (i.e., someone who inherited the account because they were listed as a beneficiary).