What Duration Means
Duration is a measure of how sensitive a bond's price is to changes in interest rates. It is expressed in years, but it is not the same as the time until a bond matures. Instead, duration estimates the weighted average time it takes to receive a bond's cash flows, and it also serves as a shorthand for interest-rate risk. A common version, modified duration, translates that idea into a percentage: a bond with a modified duration of 5 is expected to fall roughly 5 percent in price if interest rates rise by 1 percentage point, and to rise by roughly the same amount if rates fall.
Why It Matters
Bond prices and interest rates generally move in opposite directions. When rates rise, existing bonds paying lower coupons become less attractive, so their prices tend to drop. Duration gives you a single number to compare that risk across different bonds. Longer-duration bonds swing more when rates move, while shorter-duration bonds are steadier. Investors use duration to align holdings with their time horizon and their tolerance for price swings. If you may need your money soon, a lower duration usually means fewer surprises. You can compare fixed-income tools and ideas further in our investing articles.
A Simple Example
Imagine two bonds. Bond A has a modified duration of 2 years, and Bond B has a modified duration of 8 years. If market interest rates suddenly rise by 1 percent, Bond A might lose about 2 percent of its price, while Bond B might lose about 8 percent. Same rate move, very different impact. This is why long-dated bonds can feel volatile even though they are often considered conservative instruments. The trade-off is that longer duration sometimes comes with a higher yield to compensate for that added price sensitivity.
Common Mistakes
A frequent error is confusing duration with maturity. A 30-year bond has a 30-year maturity, but its duration is usually shorter because coupon payments return cash along the way. Another mistake is assuming duration is exact. It is a linear approximation that works best for small rate changes; for larger moves, a refinement called convexity improves the estimate. Investors also forget that a bond fund has an average duration that shifts over time as holdings change, so yesterday's figure may not match today's.
What to Verify Before Acting
Before relying on duration, confirm which measure is quoted, since Macaulay duration and modified duration are calculated differently. Check whether the number applies to an individual bond or an entire fund, and review the fund's current fact sheet for the latest figure. Consider how duration interacts with your broader asset allocation rather than viewing it in isolation. You can also explore how holding costs factor into fixed-income decisions using our cost of trading tool. Duration describes interest-rate sensitivity only; it does not capture credit risk, liquidity risk, or the chance that an issuer fails to pay. Always read the full risk disclosures for any specific bond or fund before acting.