The RMD is the amount that Traditional, SEP, SIMPLE IRA owners and qualified plan participants must begin distributing from their retirement accounts in the year in which they reach 70.5. The RMD must then be distributed each subsequent year.
The standard deadline for taking your RMD is December 31st. However, you can use a one time exemption for your first RMD and delay until April 1st of the following year. If you choose to utilize this deferral you will have to take both your first and second year distributions that year.
The amount of your RMD is calculated by dividing the year end value of all of your IRAs by your distribution factor. Your distribution factor can be found using the IRA Uniform Lifetime Tables which are prepared by the IRS.