I was in the mood for a little napkin math today so picked up on the line from last night’s debate from Gov. Romney stressing that he would eliminate taxes on the savings of middle-class families. In this case, middle class families consists of people making less than $200,000.

“No tax on your savings. That makes life a lot easier. If you’re getting interest from a bank, if you’re getting a statement from a mutual fund or any other kind of investment you have, you don’t have to worry about filing taxes on that, because there’ll be no taxes for anybody making $200,000 per year and less, on your interest, dividends and capital gains. Why am I lowering taxes on the middle-class? Because in the last four years, they’ve been buried. And I want to help people in the middle class.”

What’s the math on that?

Searching for the best savings rate online, the major non brick-and-mortar banks are offering about .75% annual return.

The site, Statistic Brain, says the average amount Americans have stashed in a savings account is $3,800.

According to this calculator, that yields about $28.59 a year. Here, you can calculate yours too…

Interest Income Calculator

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Interest income is taxed as ordinary income, so the amount of tax depends on your tax bracket.

The highest bracket under the plan taxes these things at 33%. So, if you made $199,999, you save $9.53 a year.

The average American household income, however, is $44,000. Assuming there’s no reduction in the adjusted gross income (highly unlikely), the interest income is taxed at 15 percent. So the proposal saved a family $4.29 a year.

But 25 percent of households in the U.S. have no savings at all. And the average retirement savings in a household is $35,000.

If all of that were shoved into a savings account (unlikely), it would yield about $253 a year in interest and the tax on the highest earners in Gov. Romney’s definition of middle class would be $83.49. But, of course, many retirement funds are in accounts that pay no taxes until they’re tapped after age 65, at a lower tax rate.