Why Bond Prices Fall When Interest Rates Rise
Every beginner in fixed income hits the same wall: “If a bond pays a guaranteed coupon, why does its price change at all? And why does it fall when rates go up?” This article answers that question step by step, with numbers. No jargon until it earns its place.
Start with a simple example
Suppose you buy a bond today with these terms:
- Face value: ₹1,000
- Coupon: 7% per year (₹70/year)
- Maturity: 3 years
- Price you paid: ₹1,000 (at par)
Everything looks fine. You will receive ₹70 every year for three years, then get your ₹1,000 back. Your yield is 7%.
Now suppose one year later, the RBI raises rates. New bonds of the same type are now being issued at 8% coupon. That means any investor who buys a new bond today earns ₹80/year on ₹1,000. Your bond still only pays ₹70/year.
Your bond is now less attractive than a new bond. If you tried to sell it in the market today, no rational buyer would pay ₹1,000 for a bond yielding 7% when they could buy a new one at 8%. They would only buy your bond at a discount — a lower price that compensates for the lower coupon.
The market adjusts the price of your bond downward until its effective yield matches the new market rate. Price fell. Rates rose. That is the relationship.
The maths behind it (keeping it simple)
A bond’s price is the present value of all its future cash flows, discounted at the current market yield. When the market yield rises, you divide by a bigger number, so the present value falls.
For our 3-year, 7% bond, with 2 years remaining and a new market yield of 8%:
| Year | Cash flow | Discount factor (8%) | Present value |
|---|---|---|---|
| 1 | ₹70 | 1 ÷ 1.08 = 0.926 | ₹64.81 |
| 2 | ₹1,070 (coupon + principal) | 1 ÷ 1.08² = 0.857 | ₹917.00 |
| Bond price | ₹981.81 | ||
You paid ₹1,000. If you sold now, you would receive approximately ₹982. You have a paper loss of ₹18 because rates moved against you by just 1 percentage point.
The flip side: rates fall, prices rise
The same logic works in reverse. If the RBI cuts rates to 6%, new bonds yield less than your 7% bond. Your bond becomes more valuable — buyers will pay a premium to own the higher-coupon stream. Price rises.
This is exactly what happened during 2020–2021, when the RBI cut the repo rate sharply in response to the pandemic. Long-duration G-Sec holders saw significant price appreciation — on paper. Investors who held to maturity never felt any of this; they simply received their coupons and principal as contracted.
Duration: how sensitive is a bond to rate changes?
Not all bonds react equally to a rate change. The key variable is duration — a measure of how long, on average, it takes to get your money back (weighted by cash flows).
Two rules of thumb:
- Longer maturity = higher duration = bigger price swing. A 20-year G-Sec will lose far more value on a 1% rate rise than a 1-year T-Bill.
- Higher coupon = lower duration. A high-coupon bond returns more of your money earlier (via coupons), so you are less exposed to rate moves on the principal.
Modified duration gives you a direct estimate: if a bond has a modified duration of 5, a 1% rise in rates will cause approximately a 5% fall in price. A bond with duration 2 would only fall about 2% for the same rate move.
| Bond type | Approximate duration | Price drop on 1% rate rise |
|---|---|---|
| 91-day T-Bill | ~0.25 years | ~0.25% |
| 3-year NCD | ~2.5 years | ~2.5% |
| 10-year G-Sec | ~7 years | ~7% |
| 30-year G-Sec | ~14 years | ~14% |
What this means if you hold to maturity
Here is the part most people miss: if you hold a bond to maturity, interest rate moves do not affect your actual return. You will receive every coupon as contracted and get your face value back at maturity, regardless of what market prices did in between.
Price volatility only matters if you need to sell before maturity. For retail investors who treat bonds as a fixed-income hold to maturity, the rate-price relationship is mostly theoretical — unless they need to exit early.
The practical exception: if you hold a bond fund (mutual fund or ETF), you do not hold individual bonds to maturity. The fund’s NAV will fluctuate with rates even if you intend to stay invested. This is why long-duration bond funds can have equity-like volatility in a rate-hiking cycle.
Reinvestment risk: the other side of the coin
When rates fall, your bond price rises — but the coupons you receive will be reinvested at lower rates. This is reinvestment risk: the total return of a bond over its life depends not just on the coupon but on what you earn by reinvesting those coupons.
YTM calculations assume you reinvest every coupon at the same YTM rate. In practice, this almost never happens. It is one reason why YTM is a useful benchmark, not a guaranteed return.
The Indian context right now
The RBI’s monetary policy committee sets the repo rate, which anchors short-term rates. The yield on 10-year G-Secs is the benchmark for longer-term borrowing in India. When the RBI was in a rate-hiking cycle (2022–2023), longer-duration G-Sec prices fell. When the RBI pivoted to cuts, longer-duration bonds rallied.
For retail fixed-income investors, the practical takeaways are:
- If you think rates are near a peak, locking in a long-duration G-Sec lets you benefit from both a high coupon and potential price appreciation if rates fall.
- If you are uncertain about the rate path, shorter maturities (1–3 years) reduce price risk — you get your money back sooner and can reinvest at whatever rate prevails.
- If you are buying and holding to maturity, focus on the yield and the credit quality, not the mark-to-market price.
None of this is a recommendation on what to do. It is a framework for thinking about the rate environment when making your own decisions.
Related reading: How RBI repo rate changes affect bond prices · See today's yield curve →