A RMD is the required amount that Traditional IRA owners and qualified plan participants must start distributing from their retirement accounts by April 1 following the year that they turn 73. RMD amounts must then be withdrawn every year after. Generally, RMDs apply only to Traditional, SEP, and SIMPLE IRAs—not Roth IRAs.
Your RMD is based on your age, your IRA’s previous year account balance, and a “life expectancy factor” that is provided by the IRS. The institution(s) where you hold your account(s) can calculate your RMD. Institutions cannot, however, see IRAs you may hold elsewhere, so ultimately, it is your responsibility to determine the total RMD for all of your accounts.
The IRS documentation on RMDs
can be found here, and should be consulted annually.