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28.08.2023
Bond Maths: How to Calculate Yield
Bond Maths: How to Calculate Yield
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Key thoughts

  • Yield shows how much your capital invested in a bond will grow per year.

  • Yield is not equal to coupon rate. They are equal only if a bond is traded at price of 100%.

Yield is also called yield to maturity, yield to worst or yield to call.

And it's the most important metric anyone investing in bonds will want to know. It tells you how much you would earn, on an annualised basis, if you held a bond until maturity.

Example: a bond with 3 years to maturity is trading at a yield of 5%. This means that if you buy this bond, the money you invest will grow at a rate of 5% per year for the remaining 3 years to maturity.

Have you noticed the italicised part of how we define yield? It really is important. Because if you want to sell the bond before maturity, the price will almost certainly be different from 100% (or par) and that will affect your financial outcome.

Hey, but why isn't yield equal to coupon?

They would indeed be equal at price = 100%, because interest is accrued at a coupon rate on a par value, and the amount you will receive back at maturity is exactly equal to the price you paid when you bought the bond. In cases where the price is not equal to par, your yield would be higher or lower than the coupon rate. 

So how do you calculate yield? Let's give you a rough but accurate way to calculate it in your head.

Formula for calculating yield.

The first component is the amount of interest income we will receive each year relative to the price we actually paid.

The second component is the amount of the capital gain (or loss) that we will receive on an annualised basis until the maturity date.

The (100% - Clean Price) part of the second component is the difference between what the issuer will pay us at maturity and our purchase price. If the price is less than 100%, the bond is said to be trading at a discount. In this case, we will make a profit if we hold the bond until maturity. If the price is above 100%, the bond is trading at a premium.

Example:

What's the yield on the BNP bond trading at 98.9% on 1 August 2023? The coupon rate is 2.375%. The bond matures on 20 May 2024.

How to calculate yield example.

Yield is traditionally calculated using a more sophisticated formula and may differ slightly from this method. That's why we have calculated the yield in Bondfish for you.

Bondfish calculated yield.

 

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.