Back
28.08.2023
Bond Maths: How to Calculate Duration
Bond Maths: How to Calculate Duration
388

Key thoughts

  • Duration is a measure of a bond's interest rate risk.

  • It shows how much the price of a bond will fall or rise if the level of market interest rates changes.

  • For a typical fixed-rate bond, duration can be roughly estimated as the time from today to maturity in years.

You need to know the duration of a bond to understand the level of interest rate risk associated with it. This is the risk that the price of a bond will fall of rise if the market interest rates changes.

Specifically, duration measures how much the bond will fall (or rise) in price if its yield changes by 1%. It is the weighted average time in years until all bond cash flows arrive.

For a typical fixed-rate bond, duration can be roughly calculated as the time from today to maturity in years.

Example:

What's the duration of the BNP bond on 1 August 2023? The bond matures on 20 May 2024.

The duration of the bond is around 0.8 years, i.e. the period from 1 August 2023 to 20 May 2024.

In reality, the duration will certainly be shorter than this rough calculation, at least because it does not take into account the time until the intermediate coupon payments.

Generally, the longer the time to maturity and the higher the coupon, the higher the duration.

Also remember that if you are absolutely certain that you will hold a bond to maturity, then interest rate risk and duration are irrelevant to you. You will receive the yield at which you bought the bond. The only risk that matters to you in this case is the credit risk, i.e. whether or not the issuer goes bankrupt during the life of the bond.

This article does not constitute investment advice or personal recommendation. Past performance is not a reliable indicator of future results. Bondfish does not recommend using the data and information provided as the only basis for making any investment decision. You should not make any investment decisions without first conducting your own research and considering your own financial situation.