FXAIX vs MGK: 48% overlap
Fidelity 500 Index and Vanguard Mega Cap Growth ETF share 48.0% of their portfolios by weight — computed as Σ min(wA, wB) over every holding both funds own.
Different holding dates. These holdings were published about 4 months apart — FXAIX as of 2026-02-28, the rest through 2026-06-30. Each fund is compared using its most recent file, so any trading in between shows up as a difference.
You would hold two tickers and get the diversification of 1.5. Two funds that shared nothing would score 2.0; two identical funds score 1.0.
Top shared holdings
FXAIX and MGK hold 53 of the same securities. The ten contributing most to the overlap figure:
| Holding | in FXAIX | in MGK | Δ |
|---|---|---|---|
| NVDA | 7.3% | 13.2% | 5.9% |
| AAPL | 6.6% | 12.1% | 5.5% |
| MSFT | 5.0% | 7.5% | 2.5% |
| AMZN | 3.5% | 4.4% | 1.0% |
| GOOGL | 3.1% | 5.9% | 2.8% |
| AVGO | 2.6% | 4.3% | 1.7% |
| GOOG | 2.5% | 4.6% | 2.2% |
| META | 2.4% | 4.1% | 1.7% |
| TSLA | 1.9% | 3.9% | 2.0% |
| LLY | 1.4% | 3.4% | 2.0% |
Where FXAIX and MGK differ
Sector weights as a share of each fund, ordered by the size of the gap rather than the size of the sector — two funds that overlap heavily still usually diverge somewhere.
| Sector | FXAIX | MGK | Δ |
|---|---|---|---|
| Information Technology | 31.8% | 58.6% | −26.8pp |
| Financials | 12.0% | 4.0% | +8.0pp |
| Industrials | 8.3% | 2.6% | +5.7pp |
| Communication Services | 10.5% | 16.2% | −5.7pp |
| Consumer Staples | 5.4% | 0.4% | +5.0pp |
| Health Care | 9.6% | 4.9% | +4.7pp |
| Energy | 3.4% | 0.0% | +3.4pp |
| Unclassified | 3.3% | 0.0% | +3.3pp |
Δ is FXAIX minus MGK, in percentage points. Sector data is not published by every issuer, so “Unclassified” is a real category rather than a gap in the table.
What each fund holds alone
52.1% of FXAIX by weight, held in no part of MGK.
2.4% of MGK by weight, held in no part of FXAIX.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| FXAIX | MGK | |
|---|---|---|
| Top 10 holdings | 36.4% | 63.5% |
| Positions held | 506 | 57 |
| Cost per $10,000 held, per year | $1 | $5 |
Cost is the expense ratio applied to $10,000; it excludes any brokerage commission, bid-ask spread or tax consequence. Figures are facts about the funds, not a suggestion about which to hold.
Frequently asked
How much do FXAIX and MGK overlap?
FXAIX and MGK overlap 48.0% by portfolio weight — moderate overlap. They share 53 holdings. The figure comes from current issuer holdings files (FXAIX as of 2026-02-28, MGK as of 2026-06-30).
How is the overlap between FXAIX and MGK calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If FXAIX holds a stock at 6% and MGK holds the same stock at 4%, 4% counts as shared. The result is bounded between 0% and 100%, and it is computed after looking through any fund-of-funds to the underlying holdings.
Is it redundant to hold both FXAIX and MGK?
That depends on your goals — we state facts, not advice. At 48.0% overlap, each fund still contributes meaningfully distinct exposure.
What does FXAIX own that MGK doesn't?
FXAIX holds 506 positions and MGK holds 57; 452 of FXAIX's positions don't appear in MGK at all, and they are 52.1% of FXAIX by weight.
You probably hold more than two funds
This page compares FXAIX and MGK. Paste your whole portfolio — brokerage, 401(k), IRA — and see the overlap across every fund at once, plus what you actually own underneath them and your own Effective Funds number. Free, no account, nothing stored.
X-ray my portfolio — free →Watch FXAIX vs MGK
We re-read both funds’ published holdings every weeknight. Leave an address and we'll tell you when what's inside actually changes.
Not sending yet — email alerts are built but switched off, and you'll be among the first when they turn on. No spam, one-click unsubscribe.
Related comparisons
Sources: issuer holdings files, FXAIX as of 2026-02-28, MGK as of 2026-06-30. Weights are fractions of each fund. Diagnostics, not advice.