By JANE SASSEEN
Yahoo! Politics

Just how much do you spend to foot the bill for U.S. troops in Iraq and Afghanistan? What's your share of the tab for interest on the national debt? How about to fund Medicare and Social Security, or to support foreign aid or the FBI?

With Tax Day upon us and Washington consumed by an intensifying battle over government spending -- a fight that's likely to be at the heart of the 2012 election — it's surprising just how little most taxpayers know about where their money goes.

The simple truth is most of us don't have any idea how much we each spend personally on government services like the military, the national parks or National Public Radio. Nor do we have a clear picture of how Uncle Sam divvies up the money we send him every year.  That makes it harder to understand the real choices the country faces as Congress and the President debate how to get our fiscal house in order.

To help U.S. taxpayers figure things out, a prominent centrist think tank called Third Way has come up a "taxpayer receipt" that allows you to see exactly where your tax dollars go. Plug the amount you paid in federal income and payroll taxes into Third Way's interactive calculator and the resulting receipt will tell you — down to the penny -- just what you paid for those U.S. troops or to keep the parks up and running.

The results can be quite illuminating. Take a typical married couple with two kids who earn the median U.S. income, $69,800. After taking standard deductions, they would pay federal taxes of $6,993. Where does their money go?

The biggest chunk — some 20.4%, or $1430.03 -- goes to Social Security. Defense comes in a close second. Our average family would pay $1,410.59 to fund the military — fully 20.2% of the total they send to Uncle Sam.

How about Homeland Security and Law Enforcement, which includes everything from the Coast Guard and the FBI to the U.S. Courts and immigration system? Just 2.4% of our average family's tax bill — only$167.95 — goes to pay for those.

As for foreign aid? They lay out just $39.60 a year. While many people think cutting foreign aid would solve our fiscal woes, it's less than 1% of what Uncle Sam spends.

Here's a look at how the rest of our average family's tax bill would break down:

Now for the fun part: Want to calculate exactly how much you pay for different government services? You can find Third Way's interactive tax receipt calculator available at their website. Add up what you paid in federal income taxes along with the payroll taxes you contributed to fund Social Security, enter the total in their calculator, and your own personalized receipt will come up. The White House liked the idea so much that they've launched their own version, called the 2010 Federal Taxpayer Receipt, as well.

On the Third Way site, there's plenty more information available, as each of the broad expenditure categories is broken into more detail. Of the 20.2% of your tax bill that goes to defense, you can see how much you're paying for Iraq and Afghanistan, how much goes to the CIA, or how much helps keep nuclear weapons safe.

Under the Arts & Culture tab, you can check out your share of the bill for the National Endowment for the Arts or for the Corporation for Public Broadcasting — the parent company to NPR.

So go ahead and play with the calculator. See what surprises you find.  Then come back and tell us what you learned in the comments below, or join the conversation on the Yahoo! Politics Facebook page.

Jane Sasseen is the editor-in-chief of politics and opinion at Yahoo! News.