Duration
A measure of how sensitive a bond's price is to a change in interest rates.
Formula
Approximate Price Change % = -Modified Duration x Change in Yield in percentage points
Unit
years
In depth
Duration is the single most important number in fixed income, because it converts a change in yields into a change in price. It is expressed in years but is not a maturity: it is the weighted average time to receive the bond's cash flows, which for a coupon bond is always shorter than its maturity. Higher coupons shorten duration, since more of the money arrives earlier, and zero-coupon bonds have duration exactly equal to maturity. A fund's duration tells you immediately how much a rate move will cost, which is why it is disclosed monthly for Indian debt funds.
Worked example
A bond fund with a modified duration of 5 loses about 5 x 1 = 5% of its value if yields rise one percentage point. On a 7.2% portfolio yield, that erases roughly eight months of income in a single move.
Illustrative figures, chosen so the arithmetic is easy to follow. Not a live price and not a valuation of any company.
Educational reference only
This entry explains what “Duration” means. It is not investment advice and not a recommendation to buy or sell any security. Any numbers above are illustrative, not live prices, and nothing here predicts price direction or rates a stock. Consider your own circumstances and consult a SEBI-registered investment adviser before acting.