NEW YORK (CNN/Money) - I own several bond funds and I'm wondering whether their prices could drop off the scale overnight. Is there a way for me to tell how volatile they are?

-- Julian Dupont, Chicopee, Mass.

Let me start by saying I think you're asking an excellent question -- a question that many of the people who stampeded into the bond market as a reaction to stock market losses ought to be asking themselves.

With interest rates at 40-year lows, the bond market has had a great run the past couple of years. But that trend can't continue forever, and now is an ideal time to size up your risk should the bull market in bonds turn into a rout.

Basically, there are two types of risk in bond funds. The first is known as credit risk, or what I prefer to call "deadbeat" risk.

It is the risk that the bond issuer might be unable to make timely interest payments on the bond and/or repay the principal when the bond comes due. You don't have to worry about this risk with Treasury bonds because we all know that Uncle Sam pays his debts (or, more accurately, gets us to pay them).

But you do have to think about credit risk with corporate and municipal bonds.

The easiest way to assess the credit risk on an individual bond is to check the rating it has received from a bond-rating company like Standard & Poor's or Moody's. The higher the rating, the less chance there is of a default.

In the case of bond funds, however, it would be impractical for you to attempt to look up the rating of each bond the fund owns. So in that case you evaluate the credit quality of the fund by looking at the credit quality of the overall portfolio.

The second type of risk in a bond is interest-rate risk -- that is, the risk that as interest rates rise, the value of your bond will fall. Generally, the longer the maturity of your bond, the more sensitive the bond will be to interest-rate movements, which is to say the more value it will lose when rates rise and the more value it will gain when rates fall.

So looking at the term remaining until a bond is repaid will give you an idea of how volatile the bond's price will be.

But, for a variety of technical reasons, maturity is not a very exact gauge of interest-rate sensibility. Which is why most bond market pros use a measure known as "duration," or a gauge of volatility that not only takes into account the bond's term but also its coupon rate and the timing of the bond's payments.

The other neat thing about duration is that, once you know it, you can get a pretty decent idea of how a bond will react to rising or falling rates. If a bond has a duration of, say, eight years, then a one percentage point rise in interest rates will cause the bond's price to fall roughly 8 percent.

If rates jump two percentage points, the bond will lose roughly 16 percent of its value (or rise roughly 16 percent if rates fall two percentage points).

Again, in the case of a bond fund, you can't determine the duration of every single bond in the portfolio. But by looking at the duration of the portfolio overall you can get a very good sense of how the fund will fare when interest rates rise or fall.

At this point, I imagine you're saying, Great, I should be looking at the ratings of the bonds in the fund and the average duration of the bond fund...But how in the world do I come by such information? Ah, did you really think I'd leave you without telling you where to find such valuable stats?

The easiest way to get this data is to plug the ticker symbol for your bond fund into the QUOTE engine that appears just below the CNN/Money logo on virtually every page of our web site. (If you don't know your fund's ticker symbol, click on the Symbol Look-Up link). That will bring you to a Snapshot Report for the fund.

If you then click on the "Portfolio link" at the top of the report, you will come to a page that provides a slew of stats about the fund, including the fund's average duration, its average credit quality rating and a percentage breakdown of the fund's portfolio by various ratings grades from the top of the credit quality scale (AAA) to the bottom (below B).

This breakdown will also show the percentage of U.S. government bonds in the portfolio and the percentage that are not rated. In short, you'll have a neat little statistical portrait that illustrates in an easy-to-understand way what kind of credit risk and interest-rate risk you're taking on with your fund.

If for some reason your bond fund isn't listed or this information isn't available for your fund, you can call a customer service rep for the fund (or the person who sold you the fund, if it's a load fund) and ask for the same information.

I can't say that every bond fund rep or sales person will provide this info (or provide it exactly in the format we do). But I can say that if I owned a bond fund that couldn't come up with some reasonable way of estimating the credit-quality and interest-rate risk, I'd definitely consider moving my money to a fund that does.

Walter Updegrave is a senior editor at MONEY Magazine and is the author of "Investing for the Financially Challenged."