NEW YORK ( TheStreet) -- In order to do an apples-to-apples comparison between the yield on a municipal bond and a taxable bond, you have to calculate either the taxable-equivalent yield of the muni bond or the after-tax yield of the taxable bond.Unfortunately, the instructions can't be boiled down to two simple equations because not all munis are totally tax-free (some are subject to state income taxes) and not all taxable bonds are totally taxable (Treasury bond, note and bill interest are exempt from state income taxes). However, there are a finite number of scenarios you might encounter. So let's run through them. In all examples, 31% represents the marginal federal tax rate and 6% represents the state marginal tax rate. When you do these calculations for yourself, use your own rates. The examples assume that your state taxes the interest on muni bonds issued outside your state. Most states do, but not all do (Indiana doesn't). Some states (Texas, Washington) don't even have an income tax.