How is the RMD computed on a yearly retirement plan distribution?

What plan is it from?  An IRA or a pension?  When you turn 73 it will ask if you took the RMD.  Oh what code is in box 7?  

For a pension, Say all of it is the RMD.   If you need to take the RMD it will ask you if it is the RMD.  Say yes.  Anything your pension pays you is considered to be the  RMD.  Traditional pensions automatically fulfill the rules of an RMD. So for the RMD question put in the same amount as box 1.

Generally, a 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 that the IRS publishes in Tables in Publication 590-B, Distributions from Individual Retirement Arrangements (IRAs).

There are a plethora of websites that have online RMD calculators you can use to calculate your RMD.  This list includes Charles Schwab, Fidelity, E*Trade, New York Life, Investor.gov