What is Interest Rate Risk? Meaning, Definition & How It Works
Index funds meaning is simpler than it sounds. Rather than paying a fund manager to research and pick stocks, an index fund buys every stock in a chosen index, in the same proportion as that index. If the Nifty 50 puts around 10% of its value in one large bank, the index fund tracking it puts roughly 10% of its money in that same bank.
The idea began abroad in the 1970s, when the first retail index fund was launched in the United States. India took longer to warm up to it. UTI launched one of the country’s earliest index funds in 2000, tracking the Sensex, but index funds in mutual funds portfolios stayed a small, overlooked corner of the industry for years. That changed as actively managed large cap funds struggled to beat their benchmarks consistently, and as the Securities and Exchange Board of India (SEBI) tightened fund categorisation and cost disclosure rules, making it easier to compare passive options on a level footing.
Today, an index fund is one of the more common ways for a new Indian investor to get equity exposure, alongside the other structured, formula-based products covered in Zenith’s guide to mutual funds in India. It sits at the opposite end of the spectrum from active management, where a fund manager researches and picks individual stocks rather than simply copying a benchmark.
Did You Know? According to AMFI’s own monthly note, total passive fund assets in India, which include index funds, ETFs and index fund of funds, stood at over Rs 14 lakh crore in March 2026, more than 23% higher than a year earlier. |
How Does an Index Fund Work?
An index fund’s job is to copy, not to choose. A stock exchange index provider, such as NSE Indices or BSE, first decides which companies belong to an index and how much weight each one gets, usually based on free-float market capitalisation (the value of the shares that are actually available for public trading). The fund manager then buys those same companies in those same weights and holds them.
When the index changes, the fund follows. Indices such as the Nifty 50 are reviewed and rebalanced twice a year, in March and September, when companies can be added or dropped based on set rules. The fund manager adjusts the portfolio to match, ideally within a few trading days of the index change.
[INFOGRAPHIC: How Index Funds Work — diagram/flowchart]
The gap between what the index earns and what the fund actually delivers to investors is called tracking error. It creeps in through small drags such as the fund’s expense ratio, cash held back for daily redemptions, and the short lag before rebalancing. A well run index fund tracking a broad, liquid index like the Nifty 50 usually keeps this gap small.
Pro Tip When two index funds track the same index, the one with the lower tracking error, not just the lower expense ratio, usually gives the closer match to the actual index return. |
Example with Real Numbers
Imagine Vikram, a 42-year-old bank manager in Ahmedabad, wants equity exposure without picking individual stocks himself. He starts a SIP of Rs 5,000 a month in a Nifty 50 index fund.
Given • Monthly SIP amount: Rs 5,000 • NAV on the first instalment: Rs 100 per unit • Units bought in month one: 50 |
As the Nifty 50 rises or falls, the fund’s NAV moves with it, minus a small expense ratio. If the NAV climbs to Rs 115 by the sixth instalment, that month’s Rs 5,000 buys about 43.5 units instead of 50. Over the years, Vikram ends up with more units bought when the NAV was low and fewer when it was high, a natural effect of investing a fixed sum every month rather than a lump sum.
This only shows how the mechanism works. It is not a projection of what Vikram’s fund will actually return, since an index fund’s returns depend entirely on how the underlying index performs over his investment period.
Types of Index Funds
Index funds in mutual funds portfolios are not all the same. Indian fund houses now offer several distinct types, built around different indices and different goals.
Broad Market Index Funds
These track well known, broad benchmarks such as the Nifty 50, Nifty 100, Sensex or Nifty 500. They spread money across large, established companies from many sectors and tend to be the first equity mutual fund index option most Indian investors buy.
Sectoral and Thematic Index Funds
Instead of the whole market, these track one sector or theme, such as banking, IT, energy or metals. Zenith’s coverage of the Axis Nifty Energy Index Fund NFO shows how one of these works in practice. They carry more concentration risk than a broad market fund, since a downturn in that one sector can drag down the whole fund.
Strategy or Factor Index Funds
These follow an index built around a rule other than plain market value, such as giving every company an equal weight instead of weighting by size. The Axis Nifty50 Equal Weight Index Fund NFO that Zenith covered recently is an example. It gives each of the 50 companies the same weight, rather than letting the largest few dominate the fund.
International Index Funds
These track a global index, such as the Nasdaq 100 or S&P 500, usually through a fund of funds structure that invests in an overseas ETF or index fund. They give Indian investors exposure to markets and companies not listed on Indian exchanges, though SEBI and AMFI’s overseas investment caps can occasionally pause fresh inflows into this category.
Debt Index Funds
Not every index fund is about equity. Target maturity index funds track a basket of government securities, state development loans or corporate bonds that mature around the same date, giving investors a more predictable, bond-like holding pattern.
Quick Comparison
Type | What It Tracks | Best Suited For |
Broad Market | Nifty 50 / Sensex / Nifty 500 | First-time equity investors |
Sectoral / Thematic | One sector, e.g. banking, energy | Investors with a specific sector view |
Strategy / Factor | Equal weight or other rule-based index | Investors seeking a different risk mix within large caps |
International | Nasdaq 100 / S&P 500 | Global diversification |
Debt (Target Maturity) | Government/corporate bond basket | Predictable, bond-like holding |
Key Components / What to Look For
- Underlying Index: The benchmark the fund is built to copy, disclosed in the scheme information document. Two funds tracking the same index should behave almost identically.
- Expense Ratio (TER): The annual fee, charged as a percentage of assets. Under SEBI’s Mutual Fund Regulations, 2026, Business Standard reported that base expense limits were trimmed by 10 to 15 basis points across categories, with index funds and ETFs continuing to carry one of the lowest caps of any mutual fund type.
- Tracking Error: How closely the fund’s return follows the index’s return over time. A lower number means a closer match.
- Fund Size (AUM) and Fund House Track Record: A larger, established index fund can usually manage rebalancing and redemptions with less friction than a very small, new one.
- Exit Load: Most index funds carry no exit load, or only a small one if redeemed within the first few days or weeks of investing.
- Growth vs IDCW Option: Growth reinvests any gains back into the fund. IDCW (income distribution cum capital withdrawal) pays some of it out periodically instead.
Benefits of Index Funds
- Low Cost: Because there is no manager researching and picking stocks, index funds usually charge a much lower expense ratio than actively managed equity funds, so more of the return stays with the investor over time.
- Broad Diversification in One Purchase: A single Nifty 50 index fund spreads money across 50 companies and multiple sectors, giving investors diversification instead of betting on one or two stocks.
- Transparency: The exact holdings are known in advance, since they simply mirror a public index, so there is no guesswork about what the fund actually owns.
- Accessible for New Investors: With SIPs starting from as little as Rs 100 a month in several Indian index funds, first-time investors can start small and build the habit of investing rather than waiting to save a larger lump sum.
- No Manager Selection Risk: Investors do not have to bet on picking the right fund manager, since the fund’s performance is tied to the index rather than to any one person’s judgement.
Risks & Limitations
- Market Risk: An index fund falls when its index falls, with no manager stepping in to hold cash or shift into safer sectors during a downturn.
- Tracking Error: Costs, cash held for redemptions and rebalancing lags can all cause the fund’s actual return to fall a little short of the index’s own return.
- No Chance to Beat the Market: By design, an index fund can only match its benchmark, never outperform it, since outperforming is exactly what it is not built to attempt.
- Concentration in Sectoral and Thematic Funds: A sector or theme based index fund carries more concentration risk than a broad market one, since its fortunes depend heavily on how that one sector performs.
Important A low NAV, such as Rs 10 during a new index fund’s NFO, does not make it cheaper or better value than an existing fund with a higher NAV. What matters is the index it tracks and its ongoing costs, not the starting unit price. |
Frequently Asked Questions
What is an index fund in simple words?
An index fund is a mutual fund that copies a market index, such as the Nifty 50, by holding the same stocks in the same proportion. It does not try to pick winning stocks. It simply mirrors the index’s ups and downs, at a lower cost than most actively managed funds.
How is an index fund different from an actively managed mutual fund?
An actively managed fund employs a manager who researches and selects individual stocks, aiming to beat a benchmark. An index fund skips that research and simply replicates the benchmark itself. This usually makes index funds cheaper, though it also means they cannot outperform their index the way a skilled active manager sometimes can.
What returns can I expect from index funds in India?
Returns depend entirely on the index a fund tracks and are never guaranteed. For context, the Nifty 50 Total Return Index delivered a 10-year CAGR of around 14.1% and a 5-year CAGR of around 16.5% as of late 2025, per Business Standard’s report on NSE data. Past index performance like this does not predict future returns, and an individual fund’s actual return will also be reduced slightly by its expense ratio and tracking error.
Are index funds safe for investors in India?
Index funds carry the same market risk as the shares in their underlying index, so their value can fall along with the market. They are regulated by SEBI and are generally considered lower risk than a single sectoral fund or individual stocks, but they are not risk-free and are not a substitute for a fixed deposit.
Can I start a SIP in an index fund, and what is the minimum investment?
Yes. Most Indian index funds accept SIPs, with several fund houses allowing a minimum of Rs 100 to Rs 500 a month. This makes index mutual funds in India one of the more accessible ways for a new investor to start building equity exposure gradually.
Which is the best index fund in India?
There is no single best index fund for everyone. Two funds tracking the same index, say the Nifty 50, should deliver near identical returns, so the more useful comparison is the expense ratio, the tracking error and the fund house’s track record, rather than chasing a headline top performer label. Zenith’s mutual fund advisors can help compare options against your goals.
What is tracking error and why does it matter?
Tracking error measures the difference between an index fund’s actual return and the return of the index it copies. A smaller gap means the fund is doing its one job well. Costs, cash buffers and how quickly the fund rebalances after an index change all affect this number.
When should I consider adding index funds to my portfolio?
Index funds work well as a core, long-term holding for investors who want broad equity exposure without picking individual stocks or funds, particularly for goals more than five years away. Zenith’s mutual fund advisors can help you see how index funds might fit alongside your existing investments.
Interest rate risk exists because of one simple mechanical link: when interest rates in the economy rise, the price of an existing bond falls. This happens because new bonds get issued at the higher, more attractive rate, so the market prices an older, lower paying bond down to compete with them. It is one of the core risks in Indian fixed income investing, and it affects government and corporate bonds, debt mutual funds, and, in a milder way, fixed deposits.
The Reserve Bank of India (RBI) shapes market interest rates mainly through its repo rate, the rate at which it lends short term funds to banks. When the RBI raises or holds this rate, bond yields across the market adjust, and that adjustment flows through to nearly every fixed income product an Indian investor holds. The Securities and Exchange Board of India (SEBI) requires debt mutual funds to disclose portfolio duration, so investors can judge how much interest rate risk a scheme carries before they invest.
Did You Know?
The RBI held its policy repo rate at 5.25% at its August 2026 review, the fourth straight meeting without a change, keeping short term borrowing costs steady for now (source: India Infoline).
How Does Interest Rate Risk Work?
Interest rate risk plays out through what is called the price yield relationship of a bond. A bond pays a fixed coupon, so if market interest rates rise after you buy it, newly issued bonds start offering a higher coupon than yours. Your existing bond becomes less attractive by comparison, so its market price has to fall until its yield lines up with the new, higher going rate.
How much the price moves depends mainly on two things: how much time is left until the bond matures, and how low its coupon rate is. A bond with a longer time to maturity, or a lower coupon, tends to move more for the same change in interest rates. This sensitivity is measured using a number called duration, which gives a rough estimate of how much a bond’s price will move for every 1 percentage point change in interest rates.
A fixed deposit works a little differently. Since an FD’s rate is locked in at the start, you will not see its value move up or down the way a bond’s market price does. Instead, the interest rate risk shows up as a missed opportunity. If you lock into an FD at 7% and rates then rise to 8%, you keep earning only 7% until the FD matures, missing out on the higher rate available elsewhere in the meantime.
Pro Tip:
Check the Modified Duration figure in a debt fund’s factsheet before investing. A duration of 5 means the fund’s value could move by roughly 5% for every 1 percentage point change in interest rates.
Interest Rate Risk Formula
Interest rate risk is most commonly quantified using Modified Duration, which estimates the approximate percentage change in a bond’s price for a given change in market yield.
Interest Rate Risk (Approximate Price Change) Formula: % Change in Bond Price = -1 x Modified Duration x Change in Yield Where: Modified Duration = a number showing how sensitive a bond’s price is to a 1 percentage point move in yield Change in Yield = the change in market interest rates, in percentage points |
A higher Modified Duration means a bigger price swing for the same change in rates. This section only defines the formula; the worked example below applies it with real numbers.
Example with Real Numbers
Imagine Vikram, a 50-year-old bank employee in Pune, holds Rs 5,00,000 in a 10-year Government of India bond with a Modified Duration of 7. Soon after he buys it, RBI policy action pushes market interest rates up by 0.5 percentage points. Given: Investment value: Rs 5,00,000 Modified Duration: 7 Change in yield: 0.5 percentage points (0.5%) Calculation: % Change in Price = -1 x 7 x 0.5% = -3.5% Fall in value = Rs 5,00,000 x 3.5% = Rs 17,500 This means Vikram’s bond would be worth roughly Rs 4,82,500 if he sold it in the market today. If he holds it to maturity instead, he still gets back the full Rs 5,00,000 face value, since the price fall only matters if he sells early. |
Types of Interest Rate Risk
Price Risk (Market Risk)
Price risk is the most familiar form of interest rate risk. It is the chance that a bond’s market price falls because interest rates have risen since you bought it. This only becomes an actual loss if you sell the bond before maturity; if you hold on, you still get the original face value back.
Reinvestment Risk
Reinvestment risk works in the opposite direction. When a bond matures, or pays out a coupon, you have to reinvest that money somewhere. If interest rates have fallen in the meantime, you end up reinvesting at a lower rate than before, which can reduce your future income.
Yield Curve Risk
Yield curve risk arises because short term and long term interest rates do not always move by the same amount. A change in the shape of the yield curve, for instance short term rates rising faster than long term rates, affects bonds of different maturities differently, even when the general direction of rates is the same.
Quick Comparison
| Type of Risk | When It Hurts You | Who It Affects Most |
| Price Risk | When you sell a bond before maturity after rates have risen | Investors who may need to exit before maturity |
| Reinvestment Risk | When a bond matures or pays a coupon after rates have fallen | Retirees relying on regular bond income |
| Yield Curve Risk | When short and long term rates move by different amounts | Investors holding bonds of mixed maturities |
Key Components of Interest Rate Risk
- Duration: shows how sensitive a bond or fund is to a 1 percentage point change in interest rates. A higher duration means a bigger price swing.
- Time to Maturity: bonds with more years left until maturity generally carry more interest rate risk than those close to maturity.
- Coupon Rate: bonds with a lower coupon rate tend to be more sensitive to rate changes than high coupon bonds of the same maturity.
- Prevailing Yield Level: the current level of interest rates in the economy, since a given rate move tends to matter more when starting yields are low.
Benefits of Understanding Interest Rate Risk
- Better fund selection: Understanding interest rate risk helps you pick a debt mutual fund whose duration matches your investment horizon, instead of picking one based on past returns alone.
- Protects retirement income: For retirees holding bonds or debt funds for regular income, knowing this risk helps avoid forced selling at a loss when rates rise.
- Opens a tactical opportunity: Investors who expect interest rates to fall can deliberately choose longer duration bonds or funds to benefit from the resulting price rise.
- Improves portfolio planning: Recognising this risk helps you decide how much of your portfolio should sit in short duration versus long duration debt instruments.
Risks and Limitations
- Duration is an approximation: Modified Duration estimates price moves accurately only for small changes in rates. For large rate moves, the actual price change can differ, a gap technically called convexity.
- Timing the rate cycle is hard: Even experienced fund managers cannot reliably predict the exact direction or timing of RBI rate moves, so duration based calls can go wrong.
- Selling early has other costs: Exiting a bond or fund early to avoid interest rate risk can trigger exit loads, capital gains tax, or a wider bid ask spread in less liquid bonds.
- Fixed deposits are not immune: FD holders face a milder version of this risk too, through reduced returns if they lock in a rate before rates rise, or reinvestment risk at renewal if rates fall.
Important:
A common mistake is switching to short duration funds only after interest rates have already risen sharply, which locks in the loss on the way out and lower future yields on the way in.
Also read: Zenith’s investment planning services for help matching your debt investments to your goals and time horizon.
Frequently Asked Questions
What does interest rate risk mean in simple terms?
Interest rate risk means the value of your bond or debt fund can go down when market interest rates go up. It happens because new bonds start paying more, making your older, lower paying bond less attractive to buyers. If you hold your investment till maturity, though, you still get back the original amount.
How is interest rate risk measured?
It is usually measured using Modified Duration, a single number found in a bond or debt fund’s factsheet. A higher duration means a bigger expected price swing for every 1 percentage point change in interest rates, while a lower duration means a smaller swing.
How is interest rate risk different from credit risk?
Interest rate risk is about market interest rates changing and affecting bonds broadly, while credit risk is about a specific issuer being unable to repay. A high quality government bond has almost no credit risk but still carries interest rate risk.
What causes interest rate risk to rise or fall?
It rises mainly with a bond’s time to maturity and falls with a higher coupon rate. It is also shaped by RBI policy decisions, inflation trends, and the general direction the bond market expects rates to take.
Does interest rate risk affect fixed deposits too?
Yes, though differently from bonds. An FD’s rate is locked in, so its value does not fall on paper. The risk instead shows up as an opportunity cost if rates rise after you lock in, or as reinvestment risk at a lower rate if rates fall by the time your FD matures.
How can I manage interest rate risk in my portfolio?
Common approaches include matching bond or fund duration to your investment horizon, laddering fixed deposits and bonds across different maturities, and keeping a mix of short and long duration debt so no single rate move hurts the whole portfolio.
Does interest rate risk always mean I will lose money?
No. It only turns into an actual loss if you sell a bond or exit a debt fund before maturity while rates are higher than when you invested. If you hold to maturity, or if rates move in your favour, this risk can leave your returns unaffected or even improve them.
When should I consider interest rate risk in my portfolio?
Consider it whenever you are choosing a debt mutual fund, buying an individual bond, or deciding how long to lock in a fixed deposit. It matters most if there is a real chance you might need the money before maturity, or if a large share of your portfolio sits in long duration debt.