The Difference Between Coupon and Yield to Maturity

A guide for beginning bond investors

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Beginning bond investors have a significant learning curve ahead of them, which can be pretty daunting, but they can take heart in knowing that the learning can be broken down into manageable steps. A good place to start is with learning the difference between a bond's "coupon" and its "yield to maturity." It's onward and upward after you master this.

In short, "coupon" tells you what the bond paid when it was issued. The yield—or “yield to maturity”—tells you how much you will be paid in the ​future. Here’s how it works.

Coupon vs. Yield to Maturity

A bond has a variety of features when it's first issued, including the size of the issue, the maturity date, and the initial coupon. For example, the U.S. Treasury might issue a 30-year bond in 2019 that's due in 2049 with a coupon of 2%. This means that an investor who buys the bond and owns it until 2049 can expect to receive 2% per year for the life of the bond, or $20 for every $1000 they invested.

However, many bonds trade in the open market after they're issued. This means that this bond's actual price will fluctuate over the course of each trading day throughout its 30-year lifespan.

Let's fast-forward 10 years down the road and say that interest rates go up in 2029. That means new Treasury bonds are being issued with yields of 4%. If an investor could choose between a 4% bond and a 2% bond, they would take the 4% bond every time. As a result, if you want to sell the bond with a 2% coupon, the basic laws of supply and demand force the price of the bond to fall to a level where it will attract buyers.

To put all this into the simplest terms possible, the coupon is the amount of fixed interest the bond will earn each year—a set dollar amount that's a percentage of the original bond price. Yield to maturity is what the investor can expect to earn from the bond if they hold it until maturity. 

Do the Math

Prices and yields move in opposite directions. A little math can help you further understand this concept.

Let's stick with the example from above. The yield increases from 2% to 4%, which means that the bond's price must fall. Keep in mind that the coupon is always 2% ($20 divided by $1,000). That doesn’t change, and the bond will always payout that same $20 per year. But when the price falls from $1,000 to $500, the $20 payout becomes a 4% yield ($20 divided by $500 gives us 4%).

However, the math isn't done yet, because this bond's overall yield, or yield to maturity, could be even more than 4%. This depends on how many years are left in the lifespan of the bond, and how much of a discount the investor got on the bond. In this scenario, the investor bought the bond at a $500 discount. When the bond matures, its price will move from $500 back to $1,000. Add the annual $20 payouts to the $500 principal increase, and the yield to maturity increases.

The yield to maturity is effectively a "guesstimate" of the average return over the bond's remaining lifespan. As such, yield to maturity can be a critical component of bond valuation. A single discount rate applies to all as-yet-unearned interest payments. 

It works the other way, too. Say prevailing rates fall from 2% to 1.5% over the first 10 years of the bond’s life. The bond’s price would need to rise to a level where that $20 annual payment brought the investor a yield of 1.5%. Applying this rate cut to our earlier example would give us $1,333.33 ($20 divided by $1,333.33 equals 1.5%).

Some Things to Keep in Mind When Calculating Yield to Maturity

Yield to maturity will be equal to coupon rate if an investor purchases the bond at par value (the original price). If you plan on buying a new-issue bond and holding it to maturity, you only need to pay attention to the coupon rate.

If you bought a bond at a discount, however, the yield to maturity will be higher than the coupon rate. Conversely, if you buy a bond at a premium, the yield to maturity will be lower than the coupon rate.

High-Coupon Bonds 

The yields for high-coupon bonds are in line with other bonds on the table, but their prices are exceptionally high. It’s the yield to maturity, and not the coupon, that counts when you're looking at an individual bond. The yield to maturity shows what you will actually be paid.

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