💵 Fixed Income

Bond Pricing Formula & Yield to Maturity (YTM) Calculator

How to calculate bond price and yield to maturity. Bond pricing formula using spot rates and YTM, with step-by-step calculation examples.

Key Concepts

Bond Pricing

PV of future cash flows discounted at YTM. Premium: coupon > YTM. Discount: coupon < YTM. Par: coupon = YTM.

Spot Rates

Yields on zero-coupon bonds. Used to discount each cash flow at the appropriate maturity rate.

Forward Rates

Future short-term rates implied by spot rates. No-arbitrage condition links spot and forward rates.

Flat vs Full Price

Full (dirty) price = Flat (clean) price + Accrued interest. Quoted price is usually clean.

Formulas

From this module

Bond Price (YTM)

P = Σ C/(1+y)t + FV/(1+y)n

Where: y = YTM per period

Bond Price (Spot Rates)

P = C/(1+S1) + C/(1+S2)² + ... + (C+FV)/(1+Sn)n

Where: S<sub>t</sub> = spot rate for maturity t

Accrued Interest

AI = Coupon × (Days since last coupon / Days in coupon period)

Where: Linear interpolation between coupon dates

Full Price

Full Price = Clean Price + Accrued Interest

Where: What the buyer actually pays

Master Formula Sheet -- Fixed Income

Bond Price

P = Σ[C/(1+r)ᵗ] + FV/(1+r)ⁿ

PV of coupons + PV of par

Current Yield

CY = Annual Coupon / Price

Income return only

YTM

Rate that equates PV of all CFs to price

Total return if held to maturity

Macaulay Duration

MacD = Σ[t × PV(CFₜ)] / Price

Weighted average time to receive CFs

Modified Duration

ModD = MacD / (1 + YTM/m)

Price sensitivity to yield change

Price Change (Duration)

ΔP/P ≈ -ModD × Δy

First-order approximation

Price Change (with Convexity)

ΔP/P ≈ -ModD × Δy + ½ × Convexity × (Δy)²

More accurate for large yield changes

Effective Duration

EffD = (P₋ - P₊) / (2 × P₀ × Δy)

For bonds with embedded options

Credit Spread

Spread = YTM_corporate - YTM_benchmark

Compensation for credit risk

Expected Loss

EL = PD × LGD × EAD

PD=prob default, LGD=loss given default

Decision Frameworks

When does a bond trade at premium/discount?

Use when:

  • Premium: coupon rate > market yield (investors pay extra for higher coupons)
  • Discount: coupon rate < market yield
  • Par: coupon rate = market yield

Avoid when:

  • Confusing clean and dirty prices when calculating returns

Test Your Understanding

A bond trading at a premium has:

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