Evaluating fixed-income investments requires understanding the return they offer, which can differ substantially from the stated coupon rate. The Bond Yield Calculator computes both current yield and approximate yield to maturity (YTM) so you can compare bonds on equal footing. A bond with a 5% coupon trading at $950 actually yields 6.154% to maturity, while the same bond at $1,050 yields only 3.902%.
The math behind calculating bond yields
The calculator uses two core formulas. Current yield is straightforward:
current yield = (annual coupon / current bond price) x 100
For a $1,000 face value bond with a 5% coupon at $950: ($50 / $950) x 100 = 5.263%.
The approximate YTM captures the full picture including capital gain or loss:
approximate YTM = ((coupon per period + (face value - price) / years) / ((price + face value) / 2)) x frequency x 100
For the same bond with semi-annual payments: ((25 + 5) / 975) x 200 = 6.154%.
Modified duration is computed using a present-value-weighted time approach, discounting each cash flow at the YTM rate and dividing weighted time by total present value.
Worked example: discount vs. premium pricing
| Scenario | Price | Current Yield | YTM | Total Return | Mod. Duration |
|---|---|---|---|---|---|
| Discount | $950 | 5.263% | 6.154% | $550.00 | 7.64 yrs |
| Par | $1,000 | 5.000% | 5.000% | $500.00 | — |
| Premium | $1,050 | 4.762% | 3.902% | $450.00 | 7.93 yrs |
The $100 price swing between the discount and premium scenarios creates a 2.251% YTM difference — a critical consideration when comparing bond offerings.
How maturity and coupon rate shift yields
Shorter maturities amplify the discount effect. A 5-year bond at $950 yields 7.179% vs. 6.154% for 10 years, because the same $50 gain is spread over half the time. Meanwhile, higher coupons reduce duration risk: a 7% coupon bond at $950 has a 6.94-year modified duration vs. 7.64 years for the 5% coupon — more income and less sensitivity to rate changes.