What is the duration of a zero coupon bond equal to?

The duration of a zero coupon bond is equal to its maturity because a zero coupon bond does not make periodic interest payments; instead, it is issued at a discount and matures at its face value. The only cash flow occurs at maturity, which means all the time until this cash flow happens is considered in the duration calculation. In practical terms, for a zero coupon bond, the duration is a direct reflection of the time until investors receive their return on investment, which coincides with the bond's maturity date. This characteristic makes zero coupon bonds unique in the context of duration, distinguishing them from coupon-bearing bonds where duration is typically shorter than maturity due to the presence of interim cash flows.