Units, AUM & Expense Ratio Explained
After understanding NAV, the next layer of clarity in mutual fund investing revolves around three interconnected concepts: units, Assets Under Management (AUM), and expense ratio.
These are not technical terms reserved for analysts. They directly affect how much you own, how large the fund is, and how much you pay for professional management. When properly understood, these concepts eliminate confusion around scale, cost, and performance.
Let us examine them one by one — and then connect them.
What Are Units in a Mutual Fund?
When you invest in a mutual fund, you do not buy “shares” of a company. Instead, you are allotted units of the scheme.
Each unit represents proportional ownership in the total assets of the fund.
If you invest ₹10,000 in a fund whose NAV is ₹20, you receive 500 units. If NAV later rises to ₹25, the value of your 500 units becomes ₹12,500.
Units are therefore simply the measurement of your ownership.
They do not fluctuate in number unless:
You invest more (additional units created for you)
You redeem (units extinguished)
You invest via SIP (units accumulated gradually)
The number of units you hold is important because your wealth growth depends on both:
Number of units
Growth in NAV
Ownership Clarity
Units represent your proportional claim on the entire portfolio of the mutual fund.
Understanding Assets Under Management (AUM)
Assets Under Management (AUM) refers to the total market value of all assets managed by a mutual fund scheme.
If a scheme manages ₹5,000 crore worth of securities, its AUM is ₹5,000 crore.
AUM changes due to two primary reasons:
Market movement (portfolio appreciation or decline)
Investor inflows and redemptions
A rising AUM may indicate growing investor confidence or strong performance. However, large AUM does not automatically mean better returns.
Does AUM Size Matter?
Yes — but contextually.
Large AUM can provide:
Better diversification
Lower transaction cost per unit
Operational stability
However, excessively large AUM in certain categories (especially mid-cap or small-cap funds) can create deployment challenges.
Smaller AUM may allow agility but may lack economies of scale.
AUM Misinterpretation
Do not select a fund solely because its AUM is high. Evaluate performance consistency and category suitability alongside fund size.
What Is Expense Ratio?
Expense ratio represents the annual fee charged by the mutual fund for managing your money.
It is expressed as a percentage of AUM.
For example, if a fund has an expense ratio of 1.5%, it means 1.5% of the fund’s assets are used annually to cover management and operational expenses.
These expenses include:
Fund management fees
Research costs
Administrative expenses
Distribution costs (in regular plans)
Custodian and audit charges
The expense ratio is deducted from the scheme’s assets before NAV is declared. Investors do not pay separately; the impact is embedded in returns.
How Expense Ratio Impacts Long-Term Returns
While 1% or 1.5% may appear small annually, compounding magnifies its impact over time.
Consider two funds delivering 12% gross returns:
Fund A expense ratio: 1%
Fund B expense ratio: 2%
Over 20 years, the difference in net return can significantly affect final corpus value.
Lower cost structures generally improve long-term compounding — provided performance remains comparable.
Cost Efficiency Insight
When two funds in the same category have similar strategy and performance, lower expense ratio can enhance long-term wealth accumulation.
Direct vs Regular – Expense Link
Direct plans have lower expense ratios because they exclude distributor commissions.
Regular plans include distribution costs, resulting in slightly higher expense ratios.
This difference gradually reflects in NAV divergence between direct and regular plans of the same scheme.
How Units, AUM and Expense Ratio Connect
These three elements are interrelated:
Units determine your proportional ownership.
AUM reflects total fund size.
Expense ratio determines cost deducted from AUM.
As AUM grows, cost efficiency may improve due to economies of scale. However, regulatory limits cap expense ratios based on fund size slabs in India.
Therefore, understanding all three together gives clarity on:
What you own
How large the fund is
How much you are paying
Practical Example
Suppose:
You invest ₹1 lakh
NAV = ₹20
You receive 5,000 units
Fund AUM = ₹3,000 crore
Expense ratio = 1.2%
Over time:
NAV rises to ₹30
Your 5,000 units now worth ₹1.5 lakh
The growth reflects portfolio appreciation after deducting expense ratio.
Your units remain 5,000 unless you transact further.
Final Perspective
Units measure ownership.
AUM measures scale.
Expense ratio measures cost.
Together, they form the structural foundation of mutual fund evaluation.
Understanding these concepts prevents superficial comparisons and enables more informed decision-making.
Cost matters. Scale matters. Ownership clarity matters.
When these are understood properly, fund selection becomes analytical rather than emotional.
Frequently Asked Questions
Finished reading? Mark it complete to track your growth.