Typically in a bond, we find an inverse relation between the price and the required yield. We know that the price of the bond is the present value of cash flows. If the required yield increases, the present value of the cash flow declines and hence the bond value also declines. Let us compute the relationship between the price and the required yield for a bond with a coupon rate of 10% with par value of Rs.100 maturing after 10 years for different required yields as per the table given below:
Table 1: PriceYield Relationship
Yield (in %)

Price in Rs.

4

148.70

6

129.40

8

113.40

10

100.05

12

88.70

14

79.16

16

71.53

18

64.04

Figure 1: Price/Yield Relationship for an Option Free Bond
If we plot a graph the priceyield relationship, we get a convex curve as seen above in the graph. This convexity has important implications with investment characteristics of a bond. Whenever yields in the market change, the bond prices also change to compensate the yield expectations of the investor. For example, if the coupon rate of a bond is 11% and the present market coupon rate for similar bonds is 12%, then the bond value gets depleted as it yields only 11% as against the current market yield of 12%. Conversely, if the current market yield is 9.5%, then the bond gets traded at premium as the bond under reference gives an yield of 11% as against the current yield of 9.5%. When the bond is sold below par value, then it is said to be sold at a discount. When the bond is sold above par value, it is said to be traded at a 'premium'. It can be summed up as follows:
Coupon rate = Required yield then price = Par value
Coupon rate < Required yield then price < Par (discount)
Coupon rate > Required yield then price > Par (premium).