Can someone tell how to compute a single number based on expense ratio, turnover, and possibly tax rate that can then be used to compare the net expenses one can expect to incur between two funds? If a portfolio's turnover is X then does that mean I should be prepared to pay tax on X*(my investment) annually? I will be holding the investment in a taxable account, and am looking at two funds which assume are identical except for expense ratio and turnover.
I'm going to say "no," that the question can't be answered and offer a bit as to why. The expense ratio comes 'off the top,' i.e. as dividends come in to a fund, they can be used for expenses. With little to no dividends, assets are sold as needed to pay the bills. In general, I think expenses are a known entity, i.e. you name the fund, look it up, and there it is, listed for you.
The dividends are somewhat predictable, but the capital gain distribution, resulting from turnover, not so much. In a rising market, investors are coming in, buying, and the manager is able to balance sales of winners vs losers, as would an individual. In a falling market with cash flows out of the fund, this isn't so easy, and often when 'gains' are actually created from forced sales of stocks that were held long term. i.e. turnover and the cap gain are not always related. If this wasn't the intent of your question, never mind.