Taxable Calculation for RMD

[Guest TAXMANAGER]

If I have determined that a distribution needs to be done under an RMD- how to do determine what the taxable amount is? For instance if someone has an account balance of $100,000 and 15,000 was post-tax contributions and 85,000 was pre-tax contributions and considering the factor tables and if the RMD ends up being let's say $17,000 for the current. How do you determine the taxable amount on the $17,000? Do you have to allocate the taxable amount for instance- would 15% of the $17,000 be non-taxable and 85% of the $17,000 be taxable? or Can I use the $15,000 and its nontaxable and $2,000 would be taxable.