ITOT vs SPY: how much do they really overlap?
ITOT (iShares Core S&P Total US Stock Market ETF, tracking the S&P Total Market) and SPY (SPDR S&P 500 ETF Trust, tracking the S&P 500) overlap by roughly 86% by weight. 10 of ITOT's top 10 holdings also appear in SPY. A 50/50 blend of the two behaves like about 62 equally-weighted bets (diversification grade A). In short, the two funds hold nearly the same stocks in nearly the same proportions — owning both is largely redundant.
The same companies, in both funds
These 24 holdings appear in both ITOT and SPY. The weight columns show how much of each fund each name represents.
| Holding | in ITOT | in SPY |
|---|---|---|
| NVDA NVIDIA CORP | 6.63% | 7.38% |
| AAPL APPLE INC | 5.81% | 6.47% |
| MSFT MICROSOFT CORP | 3.79% | 4.28% |
| AMZN AMAZON.COM INC | 3.19% | 3.68% |
| GOOGL ALPHABET INC CLASS A | 2.86% | 3.24% |
| AVGO BROADCOM INC | 2.45% | 2.76% |
| GOOG ALPHABET INC CLASS C | 2.29% | 2.60% |
| MU MICRON TECHNOLOGY INC | 1.78% | 2.02% |
| META META PLATFORMS INC CLASS A | 1.69% | 1.93% |
| TSLA TESLA INC | 1.62% | 1.81% |
| LLY ELI LILLY | 1.30% | 1.52% |
| AMD ADVANCED MICRO DEVICES INC | 1.30% | 1.38% |
| JPM JPMORGAN CHASE & CO | 1.20% | 1.38% |
| INTC INTEL CORPORATION | 0.90% | 0.97% |
| JNJ JOHNSON & JOHNSON | 0.84% | 0.97% |
+ 9 more shared holdings.
Only in ITOT
iShares Core S&P Total US Stock Market ETF — total US market. Its biggest holdings that SPY doesn’t have:
| BRKB BERKSHIRE HATHAWAY INC CLASS B | 1.25% |
| MA MASTERCARD INC CLASS A | 0.57% |
| KLAC KLA CORP | 0.54% |
| GE GE AEROSPACE | 0.53% |
| UNH UNITEDHEALTH GROUP INC | 0.52% |
| BAC BANK OF AMERICA CORP | 0.51% |
| HD HOME DEPOT INC | 0.48% |
| PG PROCTER & GAMBLE | 0.47% |
Only in SPY
SPDR S&P 500 ETF Trust — US large-cap. Its biggest holdings that ITOT doesn’t have:
| BRK.B Berkshire Hathaway Inc. | 1.42% |
So — nearly identical. Should you hold both?
ITOT and SPY hold nearly the same stocks in nearly the same proportions — owning both is largely redundant. If you already hold ITOT, adding SPY mostly increases your bet on the names they share rather than spreading it — a 50/50 blend still behaves like only ~62 equal positions, with the top 10 alone at 34% and the Magnificent Seven at 30%.
Holdings as of — ITOT: Jun 30, 2026 (iShares (BlackRock)); SPY: Jun 29, 2026 (State Street Global Advisors). Refreshed monthly. Overlap is measured across each fund’s largest holdings (top 50); the diffuse long tail barely moves the math.
See this for YOUR whole portfolio, free →ITOT vs SPY — FAQ
- How much do ITOT and SPY overlap?
- ITOT and SPY overlap by approximately 86% measured by portfolio weight — that is the share of the smaller fund's holdings (by weight) that also sit inside the other. 10 of ITOT's 10 largest holdings are also held by SPY. They share 24 of their listed top holdings in total.
- Is it redundant to hold both ITOT and SPY?
- Because they hold nearly the same stocks in nearly the same proportions — owning both is largely redundant, holding both is largely redundant — you mostly duplicate the same megacaps and concentrate rather than diversify. A 50/50 blend has an effective 62 positions and a A diversification grade.
- What does SPY hold that ITOT doesn't?
- SPY's largest holdings that ITOT doesn't hold include BRK.B. Its category is US large-cap, versus ITOT's total US market.
- Which is more concentrated, ITOT or SPY?
- ITOT's top 10 holdings are 58% of its listed weight; SPY's are 71%. The more concentrated fund leans harder on its largest names.