AUM in Mutual Funds Explained

In personal finance, numbers have a way of shaping behaviour long before logic steps in.

Bigger numbers feel safer. Large-cap companies are safer than small-cap and mid-cap companies.

This is also true in mutual fund investing. Among all the data points available, Assets Under Management (AUM) carries unusual weight.

A fund managing Rs 500 billion (bn) feels inherently more reliable than one managing Rs 20 bn. Investors assume the larger fund must be doing something right.

After all, why would so many people trust it otherwise?

This instinct is understandable, but incomplete. AUM is one of the most widely quoted yet poorly understood metrics in mutual fund investing.

It does not measure performance. It does not reflect risk control. It does not tell you whether a fund is suitable for your goals or your temperament. Yet, for many investors, it becomes a deciding factor.

So, let’s understand the meaning of AUM…

Meaning of AUM in Mutual Funds

AUM refers to the total market value of all investments managed by a mutual fund scheme or AMC at a specific point in time.

For instance, as of 31 December 2025, mutual funds’ AUM stood at Rs 80.2 trillion (tn), according to the Association of Mutual Funds of India (AMFI). This reflects the total fund the industry manages.

How SEBI’s TER Structure Links Fund Size to Costs

One area where AUM has a clear and measurable impact is cost.

As AUM increases, fixed expenses such as research, administration, and compliance are spread over a larger base. This often results in lower expense ratios, particularly in direct plans.

The Total Expense Ratio (TER) is regulated by the Securities and Exchange Board of India and varies by the fund the AMC manages.

Maximum TER as a Percentage of Daily Net Assets
AUM	TER for Equity Funds (%)	TER for Debt Funds (%)
On the first Rs 5 bn	2.25	2.00
On the next Rs 2.5 bn	2.00	1.75
On the next Rs 12.5 bn	1.75	1.50
On the next Rs 30.0 bn	1.60	1.35
On the next Rs 50.0 bn	1.50	1.25
On the next Rs 400.0 bn	TER Reduction of 0.05% for every increase of Rs 50.0 bn of daily net assets or part thereof	TER Reduction of 0.05% for every increase of Rs 50.0 bn of daily net assets or part thereof
Above Rs 500 bn	1.05	0.80
Source: AMFI

As you can see, lower AUM attracts a higher TER, and vice versa. As the size of a scheme within an AMC increase, the TER declines gradually.

TER has a direct bearing on a scheme’s NAV. The lower a scheme’s expense ratio, the higher its NAV. Thus, TER is an important parameter while selecting a mutual fund scheme.

Over long investment horizons, even small differences in costs can meaningfully affect outcomes.

That said, low costs achieved purely through scale cannot compensate for weak investment processes or poor risk management. Expense ratios matter, but only after strategy suitability is established.

What Moves AUM

One of the most important aspects of AUM is its dynamics. It changes constantly, often for reasons unrelated to a fund manager’s skill or decision-making.

The first driver of the AUM movement is market performance. When equity markets rise, the value of stocks held by equity funds increases. As a result, AUM rises even if no fresh money enters the fund.

Similarly, during market corrections, AUM can decline despite steady inflows.

The second driver is investor behaviour. When inflows exceed redemptions, AUM increases. When investors withdraw more money than they invest, AUM falls.

A fund can therefore see rising AUM during a bull market, even as investors exit, or falling AUM during weak markets, despite continued SIP inflows.

For investors, this distinction is crucial. A growing AUM driven by market appreciation is very different from growth driven by sustained investor confidence.

Likewise, a falling AUM does not automatically signal a problem if broader market conditions are unfavourable.

When a Higher AUM Truly Helps Investors

In some mutual fund categories, scale is clearly beneficial.

In debt funds, especially liquid, overnight, and high-quality corporate bond funds, a larger AUM improves liquidity management and lowers per-unit costs. Bigger funds are better positioned to meet redemptions without disturbing portfolio construction.

In index funds and exchange-traded funds, scale improves tracking efficiency. Tracking efficiency means how closely the fund tracks the underlying benchmark.

Very small index funds may struggle with higher tracking errors or wider bid-ask spreads. Larger funds typically execute trades more efficiently and track benchmarks more closely.

In large-cap equity funds, a reasonably high AUM is often manageable. The underlying stocks are deep and liquid, allowing fund managers to deploy capital without significantly affecting prices.

In these cases, rejecting a fund purely because it’s large may not be sensible.

When Size Starts Working Against Performance

The relationship between AUM and performance becomes more complex in mid-cap, small-cap, thematic, and sector-focused funds. These categories operate within narrower investment universes.

As AUM grows, fund managers must deploy larger and larger amounts of capital into a limited set of opportunities. This can dilute conviction, increase exposure to low-quality ideas, or force the fund to move toward larger stocks that do not fully align with the original strategy.

In small-cap funds, fast AUM growth can make entry and exit more price-disruptive, reducing return potential and increasing volatility during periods of market stress.

Thematic funds face a similar challenge. Strategies that work at smaller scales struggle to absorb large inflows without stretching valuations or straying from the core thesis.

In such cases, rising AUM is not automatically positive. It requires closer scrutiny of portfolio composition and investment discipline.

Does a Low AUM Always Signal Risk

Just as large size is not always an advantage, small size is not always a disadvantage.

A low AUM may simply indicate that a fund is new, under-marketed, or temporarily out of favour due to recent performance.

In some cases, it reflects a conscious decision by the fund house to limit inflows and protect returns.

However, persistently low AUM over long periods can raise concerns. Very small schemes may struggle with higher expense ratios, operational inefficiencies, or the risk of being merged or discontinued. Liquidity management can also become challenging if investor flows are uneven.

The key is to distinguish between a fund that is temporarily small and one that lacks long-term viability.

The Investor’s Final Takeaway

AUM reflects how much money a fund manages not how effectively it’s managed.

It’s shaped by market movements and investor behaviour as much as by investment skill. In some categories, scale improves efficiency and stability. In others, it reduces flexibility and return potential.

Investors should focus on whether a fund aligns with their financial goals, risk tolerance, and holding period, and whether its investment approach remains consistent across market cycles.

Over time, outcomes depend less on size and more on whether the fund’s scale suits its strategy.

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