Calculator Inputs
Example Data Table
| Input | Sample Value | Why it matters |
|---|---|---|
| Face value | 10,000 | Base principal amount used for coupon and redemption calculations. |
| Clean price per 100 | 102.40 | Quoted market price before accrued interest. |
| Base CPI | 250.00 | Reference inflation index at issuance or bond base date. |
| Reference CPI | 268.75 | Current settlement index used to derive today’s index ratio. |
| Real coupon rate | 1.75% | Coupon rate applied to inflation-adjusted principal. |
| Real yield | 1.20% | Discount rate for valuing real cash flows. |
| Expected inflation | 3.10% | Projection used for future indexed coupons and maturity proceeds. |
| Tax rate on coupons | 20.00% | Illustrates simplified after-tax coupon cash flow. |
Formula Used
Index ratio: Index Ratio = Reference CPI ÷ Base CPI
Adjusted principal today: Adjusted Principal = Face Value × Index Ratio
Invoice price: Invoice Price = (Clean Price ÷ 100) × Adjusted Principal
Projected indexed coupon: Coupont = Face Value × (Real Coupon Rate ÷ Frequency) × Projected Index Ratiot
Projected index ratio path: Projected Index Ratiot = Current Index Ratio × (1 + Periodic Inflation Rate)t
Nominal yield estimate: Nominal Yield ≈ (1 + Real Yield) × (1 + Expected Inflation) − 1
Break-even inflation: Break-Even Inflation = [(1 + Benchmark Nominal Yield) ÷ (1 + Real Yield)] − 1
Real price: Price = Σ[Real Cash Flowt ÷ (1 + Periodic Real Yield)t]
Macaulay duration: Duration = Σ(Time × Present Value of Cash Flow) ÷ Price
How to Use This Calculator
- Enter the bond’s face value and quoted clean price.
- Input base CPI and current reference CPI to create the present index ratio.
- Enter the real coupon rate, real yield, and coupon frequency.
- Add years to maturity and your expected annual inflation assumption.
- Optionally enter a benchmark nominal yield to estimate break-even inflation.
- Set a coupon tax rate for simplified after-tax cash flow projections.
- Choose the deflation floor option when the bond contract protects principal at maturity.
- Press Calculate to view results above the form, the chart, and the payment schedule.
- Use the export buttons to save schedule data as CSV or PDF.
Frequently Asked Questions
1. What does an inflation-linked bond calculator estimate?
It estimates today’s indexed principal, future inflation-adjusted coupons, maturity value, valuation metrics, and rate relationships between real and nominal yields using your assumptions.
2. Why do I need both base CPI and reference CPI?
Those values create the index ratio. The ratio scales the bond’s principal from its base level to the current inflation-adjusted amount used for pricing and coupon calculations.
3. Is the quoted clean price already inflation adjusted?
Usually the market quote is a price per 100 of adjusted principal, excluding accrued interest. This calculator uses that quote with today’s index ratio to estimate invoice value.
4. What is break-even inflation?
Break-even inflation is the inflation rate that makes a nominal bond and an inflation-linked bond offer comparable expected returns over the same horizon.
5. Why is nominal yield only an estimate here?
The calculator uses a Fisher-style relation between real yield and expected inflation. Actual market pricing can differ because of liquidity, taxes, seasonality, and risk premiums.
6. What does the deflation floor option do?
It prevents projected final principal from falling below face value at maturity. Some inflation-linked securities include this protection, while coupons may still follow the indexed balance.
7. Are taxes handled exactly like real bonds?
No. This page applies a simplified coupon tax assumption for planning. Real tax treatment can vary by country, account type, index accretion rules, and security structure.
8. Can I use this for TIPS, linkers, and similar securities?
Yes, for educational analysis and scenario testing. Still verify settlement lags, day-count rules, seasonal index interpolation, and accrued interest conventions from the actual instrument terms.