I’ve always wondered if I should convert my IRA or my 401k into a Roth IRA.

The key variable in this “what if” analysis is what tax bracket will you be in the future compared to now.  Recognize that tax laws can change.

Article quantifies benefit for each tax bracket
http://www.schwab.com/public/schwab/nn/articles/Roth-IRA-Conversion-Look-Before-You-Leap

Conclusion: Note that you must pay the tax from a different source.  If you pay the tax from your IRA or 401 account you will never come out ahead.  However if you pay the taxes due from some other account, and you expect to be in a lower tax bracket you could benefit. If you stay in the same bracket, you only “might” benefit from conversion.

Tax brackets.

http://taxfoundation.org/article/2016-tax-brackets

10% – $18,550
15% – $75,300
25% – $151,900

Remember, when you convert, it could push you into a higher bracket for that year.
Standard deduction and personal exemption – $12,600 married in 2016. (If neither is 65.)