AUM — assets under management — is the total market value of the investments a fund or firm manages on behalf of its clients. It's the standard measure of size in the investment industry: a $500 million hedge fund and a $10 trillion asset manager are different animals, and AUM is the number that tells you which one you're looking at.
This guide covers how AUM is calculated, why it rarely matches the value you'll see in a fund's disclosed portfolio, and what a manager's size means when you're deciding whether to follow them.
How AUM is calculated
At its simplest, AUM is the sum of the market value of everything a firm manages: stocks, bonds, cash, and other assets across all its funds and client accounts. The figure moves for two reasons — performance (the assets themselves gain or lose value) and flows (clients add or withdraw money).
There's an important catch: no single mandated formula exists. Some firms count committed-but-uninvested capital, some include leverage, and regulatory AUM (the "regulatory assets under management" in SEC filings) is calculated differently from the marketing figure in a fund's pitch deck. Treat AUM as a reliable order-of-magnitude measure rather than an audited statistic.
AUM vs 13F value: not the same number
If you compare a firm's stated AUM with the total value of its 13F filing, they will almost never match — and the gap is informative, not an error. A 13F discloses only the firm's long positions in U.S.-listed securities. Cash, bonds, short positions, foreign-listed holdings, and most derivatives sit outside the form.
So a global macro fund with $50 billion in AUM might show only a few billion in its 13F, while a long-only U.S. equity manager's 13F can capture nearly everything it runs. Portfolio values on Wall St. Rank are 13F values — the disclosed U.S. equity sleeve — which is exactly the slice relevant to stock investors following institutional money.
The $100 million threshold: when AUM triggers a 13F
AUM is also the tripwire for disclosure. Once a manager exercises investment discretion over $100 million or more in qualifying U.S. equities, it must begin filing quarterly 13Fs — within 45 days of each quarter end, as covered in our 13F filing deadlines guide. That threshold is why the 13F universe is, by construction, a census of every institutional investor of meaningful size in U.S. stocks.
Why size matters when you follow a manager
A fund's AUM shapes how it invests — and how useful its disclosures are to you:
- Big funds move slowly. A firm like Bridgewater Associates can't build or exit a multi-billion-dollar position quickly without moving the market against itself. Positions are necessarily accumulated over quarters and held on long theses — which is precisely why the 45-day disclosure lag costs followers of large funds so little.
- Big funds are pushed toward big stocks. At the scale of a BlackRock, only the largest, most liquid names can absorb meaningful allocations, so mega-cap holdings dominate. Smaller managers can take meaningful stakes in mid- and small-caps that giants can't touch.
- AUM growth is a signal in itself. A manager whose assets are compounding is delivering returns, attracting inflows, or both; steady AUM decline invites the opposite question.
AUM and fees
AUM is also the base on which managers charge. The classic hedge fund model — a management fee on assets plus a performance fee on profits, the "2 and 20" — means a firm's revenue scales with its AUM, which is why growing assets is a business goal in itself. The full fee picture, and how it shapes incentives, is covered in our guide to how hedge funds work.
Explore funds of every size
Wall St. Rank tracks the disclosed portfolios of more than 13,000 institutional managers — from trillion-dollar giants to funds just over the $100 million threshold — with filing history back to 2013, every one validated and normalized by the same pipeline (see our methodology). Browse them in the fund portfolio index, sortable by AUM, or start with the Wall St. Rank Fund Manager Index, which aggregates the most commonly held stocks across managers. For a wider view of the market, the rankings hub collects the site's stock and fund rankings in one place.
FAQ
Is higher AUM better?
Bigger isn't better or worse — it's different. Large AUM signals institutional trust and durability, but it constrains a manager to liquid mega-caps and makes outsized returns harder; smaller funds are nimbler but less proven. For followers, the more useful question is whether a manager's size fits its strategy — and whether its disclosed portfolio has performed, which is what our post-disclosure return outliers ranking measures.
Does AUM include leverage?
It depends on the firm and the context. Gross AUM can include leveraged exposure while net AUM counts only client capital, and disclosure conventions vary — one more reason to treat AUM as an approximate size measure rather than a precise accounting figure.
What's the largest hedge fund by AUM?
By most measures, Bridgewater Associates has ranked among the largest hedge funds in the world for years, with well over $100 billion under management — though rankings shift with markets and flows, and the biggest asset managers (which aren't hedge funds) are an order of magnitude larger still.
