Roth conversion calculations

I am trying to calculate the amount of a Roth IRA conversion that allows me to stay in the lowest tax bracket.  In estimating my projected taxable income, I have included taxable dividends and interest.  I also have tax-exempt dividends and interest - do these amounts need to be included in the calculation of taxable income in the determination of a potential Roth IRA conversion amount, or would these be excluded?  Thank you.