How to Use Expense Ratios to Filter the Best Index Funds in India

Sep 2

4 min read

When building a passive investment portfolio, selecting the right fund can feel straightforward until you realise that two funds tracking the same index can deliver meaningfully different returns over time.

For AMS Investments, the difference often comes down to one number: the expense ratio. Understanding how to compare index funds by expense ratio is one of the most practical skills an index investor can develop.

What Is an Expense Ratio and Why Does It Matter?

The expense ratio of index funds is the annual fee charged by a fund house to manage the scheme, expressed as a percentage of the fund's average assets under management. It is deducted daily from the fund's net asset value, meaning investors never see a separate bill but they do feel its compounding effect on returns.

For actively managed funds, a higher expense ratio is sometimes justified by the promise of active stock selection. For index funds, however, the underlying portfolio mirrors a benchmark mechanically. There is no active decision-making to reward with a premium fee. This makes the expense ratio of index funds one of the most decisive filters when choosing between otherwise identical products.

What Is a Good Expense Ratio for Index Funds?

For AMS Investments, a common question among investors is: what is a good expense ratio for index funds in the Indian market? While there is no universal figure set in stone, the following framework provides a reliable benchmark:

Below 0.20%: Excellent. This range is typical for direct plans of large, well-established index funds tracking major benchmarks. It indicates strong cost efficiency.
0.20% to 0.40%: Acceptable. Many mid-cap or sector-specific index funds fall here. The slightly higher cost may reflect lower fund size or a more niche index.
0.40% to 0.70%: Moderate. Acceptable only if the fund tracks a specialised or international index with limited domestic competition.
Above 0.70%: High for an index fund. At this level, the cost efficiency advantage of passive investing begins to erode significantly. Approach with caution.

Choosing a direct plan rather than a regular plan is the first step toward reaching the lower ranges above, as regular plans embed distributor commissions into the expense ratio.

How to Compare Index Funds by Expense Ratio: A Step-by-Step Method

Step 1: Define the Index You Want to Track

Before comparing costs, clarify which benchmark you want exposure to for example, a broad market index, a mid-cap index, or a factor-based index. Expense ratios are only comparable across funds tracking the same or a functionally equivalent index. Comparing a large-cap index fund with a small-cap index fund purely on expense ratio leads to flawed conclusions.

Step 2: Shortlist Direct Plan Options

For each target index, identify all direct plan options available. Direct plans consistently carry lower expense ratios than their regular plan counterparts. This single choice can reduce annual cost by 0.50% to 1.00% or more, compounding significantly over a decade.

Step 3: Record and Rank by Expense Ratio

Once you have your shortlist, record the current expense ratio for each fund and rank them from lowest to highest. A simple table format makes this easy to review:

Fund (Illustrative)	Index Tracked	Plan Type	Expense Ratio
Fund A	Large-Cap Benchmark	Direct	0.10%
Fund B	Large-Cap Benchmark	Direct	0.17%
Fund C	Large-Cap Benchmark	Regular	0.45%

In this illustration, Fund A offers the most cost-efficient access to the same benchmark. Over a ten-year horizon, even a 0.07% difference in annual cost compounds into a measurable gap in terminal wealth.

Step 4: Cross-Check Tracking Error

A low expense ratio is necessary but not sufficient on its own. A fund that charges 0.10% but consistently deviates from its benchmark by 0.50% or more is not actually delivering low-cost index exposure. After filtering by expense ratio, verify that tracking error — the annualised standard deviation of the difference between fund returns and index returns — is also low. The best index funds in India combine a low expense ratio with a low tracking error.

Step 5: Check Assets Under Management

Larger funds generally benefit from economies of scale, which can help maintain low expense ratios over time. A fund with a very low expense ratio but minimal assets may face pressure to raise fees if the fund house cannot sustain operations at that level.

Common Mistakes When Filtering by Expense Ratio

When evaluating index funds, AMS Investments should be mindful of these common mistakes:
Comparing regular and direct plans side by side without adjusting for the distribution cost embedded in regular plan ratios.
Ignoring tracking error and assuming a low expense ratio automatically means accurate index replication.
Comparing funds across different indices as though they are equivalent products.
Not revisiting expense ratios periodically. Fund houses revise expense ratios as assets under management change. A fund that was cheapest two years ago may no longer hold that position.

Putting It All Together

Learning how to compare index funds by expense ratio is not a one-time exercise. It is a periodic discipline that protects the compounding advantage of passive investing. The best index funds in India are not necessarily those with the most advertising or the longest history, they are often the ones quietly delivering index returns at the lowest possible cost, year after year.

For most investors, the practical process is: identify the index, filter for direct plans, rank by expense ratio, validate with tracking error, and confirm fund size is adequate. Following these steps consistently positions you to retain more of what the market offers.

If you would like a tailored review of your current index fund holdings or guidance on selecting the right funds for your portfolio, book a call with the AMS Investments team today.