Make sure that you're using the latest worksheets because the tables are updated to reflect life expectancy changes. Different situations call for different tables. For example, if you have a non-Roth IRA and the account's sole beneficiary is your spouse, and your spouse is more than 10 ...
The formula used to calculate the RMDs is the account balance as of December 31 of the previous year divided by a life expectancy factor. Three life expectancy tables are used to determine the factor: the joint life & last survivor expectancy, the uniform life expectancy, and the single life...