Yield to worst is the yield that is produced from a bond before it reaches its worse level of returns in its lifespan.
A Yield to worst is usually worked out on bonds that have more than one call date, known as callable bonds. The yield to maturity or the yield to call has to be worked out first. The lowest figure produced from these calculations is the yield to worse.
To find out more about the calculation needed to find the yield to worse we suggest looking at yield to maturity, yield to call and internal rate of return definitions.