To better understand their practical significance, here is how they differ in purpose and behaviour.
Coupon Rate: Provides a fixed return on face value and doesn't change with market conditions.
YTM: Reflects actual yield based on current price and reinvestment assumptions.
Example:
If a bond with a 10% coupon is trading at par (₹1,000), then YTM = 10%
If the same bond trades at ₹950, YTM becomes greater than 10% (you pay less but receive the same ₹100 coupon). If the bond trades at ₹1,050, YTM becomes less than 10%.
This shows how YTM adjusts based on bond price fluctuations.
Formula and Calculation
Let us break down the core formula used to calculate YTM:
YTM = [C + (F - P) ÷ n] ÷ [(F + P) ÷ 2] × 100
Where:
C = Annual coupon payment
F = Face value of bond
P = Purchase price of bond
n = Number of years until maturity
This approximation provides a quick estimation of YTM, though more accurate values use iterative methods or financial calculators.