Why Small Cap Stocks Earn a Place Beside Your US Equities
You already own the big companies. If your portfolio holds an S&P 500 index fund, the bottom rung of American business is missing or weighted so lightly it rounds to nothing.
Start with the arithmetic. On a $100,000 portfolio a 5% small cap sleeve is $5,000. Enough to move your return in a year when small cap stocks run, small enough that a 30% drawdown is minimal and can be recovered. All six funds below returned more than 32% over the trailing twelve months ended June 30, 2026.
The appeal is diversification with an economic basis under it. Investors who own only an S&P 500 fund miss small cap stocks entirely, and the risk profile is why many hesitate. Small cap stocks can earn revenue differently than mega cap stocks, carry more debt sensitivity, and respond to domestic demand rather than a global sales mix, which your US equities capture.
Size the sleeve for the drawdown, not the rally. Volatility cuts both ways, and the same volatile swing that lifts these stocks 40% takes it back. Before you invest a dollar, settle how many ETFs you need.
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What Counts as a Small Cap Stock
Ask three index providers what a small cap stock is and you get three different answers. That settles which stocks end up in your small cap ETF.
The cleanest answer comes from the Russell 2000. At the April 30, 2026 rank day, the market cap breakpoint separating large caps from small caps rose 24% to $5.7 billion, and its smallest company carried a market cap of $146.4 million.1 So within the Russell 2000 the market cap range representing small cap stocks runs from roughly $146 million to $5.7 billion.
Any fixed dollar cutoff ages badly. A rule of thumb you learned as “under $2 billion” was true against a different market cap range and stopped being true. Total market capitalization drifts upward and the small cap index redraws its boundary. FTSE Russell now reconstitutes the Russell US indexes semi-annually, changed from annual effective 2026. Set that beside what the S&P 500 actually holds and the contrast drives everything below.
The 6 Best Small Cap ETFs, Compared
The six best small cap ETFs on one page, with the metrics that decide most choices.
| ETF |
iShares Core S&P Small-Cap ETF (IJR)
|
iShares Russell 2000 ETF (IWM)
|
Avantis US Small Cap Value ETF (AVUV)
|
Vanguard Morningstar Small Cap Growth ETF (VBK)
|
Avantis International Small Cap Value ETF (AVDV)
|
Invesco S and P SmallCap Momentum ETF (XSMO)
|
| Index | S&P SmallCap 600 | Russell 2000 | Actively managed | Morningstar US Small Cap Growth | Actively managed | S&P SmallCap 600 Momentum |
| Inception | 5/22/2000 | 5/22/2000 | 9/24/2019 | 1/26/2004 | 9/24/2019 | 3/3/2005 |
| Net Assets | $112B | $82B | $29B | $25B | $19B | $3B |
| Expense Ratio | 0.06% | 0.19% | 0.25% | 0.05% | 0.36% | 0.36% |
| Holdings | 671 | 1,965 | 792 | 544 | 1,717 | 108 |
| Top Ten % | 7.32% (6/30) | 3.42% | 8.54% | 9.3% | 8.15% | 24.28% |
| 30-day SEC Yield | 1.48% (7/31) | 1.14% | 1.21% | 0.39% | 2.64% | 0.69% |
| Past Year | 37.42% | 40.59% | 39.00% | 32.73% | 34.63% | 38.60% |
| 3 year Avg. | 15.98% | 18.44% | 19.06% | 17.46% | 26.06% | 25.41% |
| 5 year Avg. | 7.30% | 6.86% | 12.29% | 5.37% | 13.81% | 12.30% |
| 10 year Avg. | 11.47% | 11.53% | Not applicable | 12.16% | Not applicable | 15.50% |
All returns are NAV basis, standardized, average annual, for periods ended June 30, 2026.
Now the part comparison tables get wrong: more holdings is not automatically more diversification. IWM holds 1,965 stocks against IJR’s 671, and the two are not nested sets. Different indexes, different breakpoints, different entry rules, and IWM’s holdings reach further down the size and liquidity scale, where trading costs run higher. The bigger number is a poor guide to risk.
Core Exposure: The Cheapest Core Small Cap ETF on the List
IJR is the plain core small cap ETF here. It tracks the S&P SmallCap 600, held 671 stocks on August 12, 2026, and charges 0.06%.2
Investors underrate this. On $10,000, 0.06% costs $6 a year against $19 for IWM. Compounding can work on your returns or on your costs, so across thirty years the cheaper small cap ETF keeps more of whatever its index delivers.
The top ten holdings account for 7.32% of assets on June 30, 2026, unconcentrated by any normal standard, though IWM’s wider net puts its top ten at 3.42%. One caution: the largest is a BlackRock cash fund at 1.96%, so these are the ten largest holdings, not the ten largest companies.
IJR’s 30-day SEC yield was 1.48% on July 31, highest of the four that print one. Small cap dividends are not the reason to own this category, though a fraction of your return arriving as cash makes volatile years easier. Start with how to invest in ETFs.
Broad Exposure: Every Small Cap the Russell Can Hold
IWM is the small cap ETF most investors picture and owns more stocks than anything else here, holding 1,965 positions on August 12, 2026, tracking the Russell 2000.3
So does owning 1,965 companies buy anything the 671 do not?
Some, and less than the count suggests. The Russell 2000 takes approximately the 2,000 smallest securities by market cap and index membership, with no profitability screen, so IWM owns companies that would fail the S&P SmallCap 600 screen at the point of addition. That widens the range of outcomes rather than raising the return you should expect. IWM led these funds at 40.59% over one year and trailed IJR over the five-year performance window, 6.86% against 7.30%, on the same inclusion policy. The fee is 0.19%, three times IJR’s, for a small cap ETF that tracks a looser small cap index. Those costs can compound the way returns do, only against you.
Value: Where Profitability Meets Price
AVUV is actively managed and does not seek to replicate an index.4 That sentence makes some investors close the tab.
Active does not have to mean a hunch. Avantis emphasizes smaller stocks trading at low prices relative to book value, weighted by a profitability screen on top. The prospectus is explicit: portfolio managers continually analyze market and financial data to make buy, sell and hold decisions. Active strategies like this track a rule set, and management still exercises judgment and risk inside it.
AVUV returned 12.29% a year over five years, ahead of every broad market index fund here, though its international peers at AVDV beat it in the same category at 13.81%, with 19.06% over three years. That performance is the case for the strategy. It held 792 stocks and charges 0.25%, low for a fund run this way. Two caveats. Both Avantis funds launched September 24, 2019, so neither has a ten-year record until 2029, and their fact sheets print dividends quarterly but no 30-day SEC yield. Want a growth tilt instead? The 6 best growth ETFs covers that side.
Growth: The Lowest Expense Ratio on the List
VBK carries the lowest expense ratio in this six-fund comparison at 0.05%, and posted the weakest five-year number of the six at 5.37%.5 Holding both together is the lesson here.
A low expense ratio buys a cheap ride on whatever the index does, never a good index for the stretch you own it, and costs alone do not predict performance. Investors in small cap growth spent five years behind small cap value, and VBK’s 5.37% against AVUV’s 12.29% is that spread. Over ten years VBK returned 12.16%, second-best in the table. Same fund, different window, opposite conclusion. Vanguard’s management tracks the Morningstar US Small Cap Growth Index, renamed from CRSP in July 2026, with holdings of 544 stocks at June 30, 2026, a top ten weight of 9.3%, quarterly dividends, and a 0.39% 30-day SEC yield. That same point runs through VOO vs VTI on the large cap side.
International: Small Caps Outside US Equities
Every fund above owns American stocks. AVDV runs the same idea outside your US equities, across developed markets, with the value and profitability tilt AVUV applies at home.
Japan is AVDV’s largest country exposure at 33.00% on June 30, 2026, roughly one third of the fund.6 That is not a country call. The strategy screens developed-market small cap stocks on price and profitability, weighted by market cap, with managers exercising judgment inside it. That figure moves as the process reruns, so investors should check it before assuming the fund they bought is the one they own later.
AVDV posted the strongest three-year performance here at 26.06%, with 13.81% over five. It held 1,717 stocks, charges 0.36%, and its fact sheet prints dividends quarterly but no 30-day SEC yield. AVDV charges the most on fees here, tied with the domestic XSMO. Those costs are real, the liquidity thinner, and both show up in what you keep. See best international ETFs.
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Momentum: Concentration as a Deliberate Choice
XSMO held 108 stocks on August 10, 2026, from a parent index of 600.7 The strategy keeps one in five of those companies for inclusion, dropping the rest on purpose.
That is a momentum strategy being honest. The index screens the parent universe for price momentum and keeps the winners, weighted on a modified market cap basis, rebalancing semi-annually either way. Sector exposure floats wherever market momentum is, so this small cap ETF tilts its sector weights heavily. The sector mix is an output, not a target.
Concentration shows in the top ten holdings, 24.28% by our own arithmetic from Invesco’s per-holding weights, so note it as derived, not an issuer number. Three times its peers here.
XSMO generated the best ten-year number in the table at 15.50%, with 25.41% over three years, on a 0.36% fee and $3.10B of net assets, smallest of these funds. Momentum works until it turns, and a 108-stock fund concentrates whatever happens next into fewer names. That is concentration risk and volatility, plainly.
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How Small Cap Index Families Disagree
Three index families draw the small cap line in three places, and your fund inherits whichever line it tracks. This is where ETF overlap stops being abstract. Two small cap ETFs can use the name and share very few stocks, which catches investors out.
The S&P Screen: Positive Earnings Required
S&P Dow Jones Indices requires GAAP net income from continuing operations to be positive for the most recent quarter and the sum of the most recent four quarters.8 That one rule breaks the category in half. Stocks burning cash do not qualify for addition. A company inside that stops earning is not automatically dropped: S&P states a constituent violating the addition criteria is not deleted unless ongoing conditions warrant a change. The S&P SmallCap 600 holds 600 companies, and an S&P index committee makes the final selection, not a pure market cap ranking.
MSCI USA Small Cap: A Share of the Market, Not a Head Count
Another route runs through MSCI. As of July 31, 2026 the index holds 1,639 constituents representing approximately 14% of US free float-adjusted market capitalization, with a median constituent of $2,560.78 million.9 The count is an output, not a target. MSCI USA Small Cap defines the segment as a share of total market capitalization, calculated from the free float and weighted by it.
Same Index, Different Fund: State Street SPDR Portfolio S&P 600
The cheapest lesson in this article: State Street SPDR Portfolio S&P 600 Small Cap ETF, ticker SPSM, tracks the identical index IJR tracks and charges 0.03%, half IJR’s 0.06%.10 Same benchmark of 600 companies, same index rules, half the costs. Check the ticker before assuming the famous fund is the cheap one.
What the Best ETFs for Small Cap Value Can and Cannot Promise
Small cap value leads this table over five years. AVUV generated 12.29% a year and AVDV 13.81%, against 12.30% for XSMO, 7.30% for IJR and 5.37% for VBK. That is a real spread, and the story most analysis of small cap stocks tells.
Here is what those numbers cannot promise.
Five years is one window. Run the comparison over ten and VBK’s 12.16% beats IJR’s 11.47%, while both value funds lack a ten-year record, each launched September 2019. Over twelve months IWM’s 40.59% leads these funds, from one of two here whose index applies no profitability screen for inclusion. Change the window and the ranking changes with it.
Past performance is the weakest evidence here, which is why the fee and the index rule carry more of this article than the returns. Five years of performance shows a strategy did what it aims to do under the conditions that existed, never that it will perform that way under yours. Success here is a decade, not a good year.
Leveraged versions exist and reset daily, so over a longer hold the compounding path can help or hurt as much as the multiple. For the best etfs on the large cap side, which is the best S&P 500 ETF covers it.
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Picking the Small Cap ETF That Fits Your Portfolio
Six funds, and not one of these small cap ETFs is right for all investors.
Want to invest in one small cap ETF and nothing to think about? IJR tracks the S&P 600 at 0.06%, and SPSM the same job at lower costs, 0.03%. Want the widest net? IWM. If the value premium is real and you aim to capture it with a systematic process, AVUV covers home and AVDV abroad. If your portfolio already tilts value, VBK balances it at the lowest expense ratio here, reflected in its 0.05% fee. XSMO is a momentum strategy, not a core holding.
Whichever of the best small cap ETFs you buy, size it to the risk you can hold through a 30% drawdown, and wait out the bad years rather than selling into them. Read the prospectus for costs and risks first. No matter how the next quarter goes, small cap investing is a decade-long position.
Check the fee and the index rule before the other metrics, then invest and leave it alone.
