How many stocks or funds do I need to be diversified?

There's no magic number: it's about variety, not count. A few broad, low-correlation funds (e.g. global stocks + bonds) can be far more diversified than twenty overlapping US equity funds.

Does adding international stocks diversify my portfolio?

Usually yes, to a degree, because international markets don't move perfectly with the US. But global correlations have risen over time, so the benefit is smaller than it once was. Check the actual correlations for your holdings.

What's a good correlation for diversification?

Lower is better. Holdings correlated near 0 (or negatively) provide real diversification; anything consistently above ~0.8 is largely redundant.

How to Tell If Your Portfolio Is Actually Diversified

6 min read · Updated 2026-06-15

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Most people measure diversification by counting holdings: “I own eight funds, so I'm diversified.” But if all eight track US large-cap stocks, that's one bet wearing eight costumes: they'll rise and fall together.

Real diversification is about how your holdings move relative to each other. This guide explains the number that actually measures it, the trap that catches even careful investors, and how to check your own portfolio in a couple of minutes.

Check your portfolio's correlations →

Diversification is about correlation, not count

Two holdings that always move together give you no protection: when one drops, so does the other. Two that move independently (or in opposite directions) cushion each other. So the question isn't “how many holdings do I have?” but “how differently do they behave?”

A classic example: an investor holding an S&P 500 fund, a US total-market fund, a large-cap growth fund, and a handful of US tech stocks feels diversified, but is really making one concentrated bet on US equities.

Correlation: the number that measures it

Correlation runs from -1 to +1 and tells you how two holdings move together:

•+1.0: they move in lockstep. No diversification benefit at all.
•Around 0: they move independently. Combining them meaningfully reduces risk.
•Negative: they tend to move in opposite directions. This is the strongest diversifier (and the rarest).

Illustrative long-run correlations between major asset classes
	US stocks	Intl stocks	Bonds	Gold
US stocks	1.00	0.85	0.10	0.05
Intl stocks	0.85	1.00	0.15	0.10
Bonds	0.10	0.15	1.00	0.25
Gold	0.05	0.10	0.25	1.00

Illustrative long-run values: real correlations shift over time and tend to rise in crises. Check your own holdings in the correlations tool.

The trap: correlations rise exactly when you need them low

Here's what catches people: correlations aren't fixed. In a calm market, two assets might look uncorrelated, but in a panic like 2008, almost everything risky falls together as investors sell whatever they can. The diversification you counted on can evaporate at the worst moment.

That's why looking at a single long-run correlation number isn't enough; it's worth checking how correlations behaved during the actual stress periods, not just on average.

How to check your own mix

Run a correlation matrix across your holdings and look for clusters of high numbers (anything consistently above ~0.8 is doing the same job). Then check rolling correlations over time to see whether your “diversifiers” actually held up during downturns.

What real diversification looks like

Genuine diversification usually means spreading across things that respond to the world differently: different asset classes (stocks, bonds, real assets), geographies (US, international, emerging) and risk factors, not five flavors of the same index. The goal isn't more holdings; it's holdings that don't all sink at once.

Try it yourself

Asset CorrelationsSee how your holdings move together and spot the overlap.Open tool →Rolling CorrelationsCheck whether correlations held up during downturns.Open tool →Factor AnalysisSee which underlying risk factors actually drive your returns.Open tool →

FAQ

How many stocks or funds do I need to be diversified?: There's no magic number: it's about variety, not count. A few broad, low-correlation funds (e.g. global stocks + bonds) can be far more diversified than twenty overlapping US equity funds.
Does adding international stocks diversify my portfolio?: Usually yes, to a degree, because international markets don't move perfectly with the US. But global correlations have risen over time, so the benefit is smaller than it once was. Check the actual correlations for your holdings.
What's a good correlation for diversification?: Lower is better. Holdings correlated near 0 (or negatively) provide real diversification; anything consistently above ~0.8 is largely redundant.

Key terms in this guide

Plain-English definitions in the Learning Hub.

Correlation →Benchmark correlation →Diversification score →Beta →

Already computed · real data

The four US funds vs the mix across assets on real data

Side by side, same dates

Four US stock funds (SPY, VTI, VUG, QQQ, 25% each) grew from $10,000 to $100,790 between Aug 2007 and Oct 2026 (12.8% a year). Its worst fall was -50%, from Oct 2007 to Feb 2009, and it took 42 months (about 4 years) to get back to that high. A mix across assets (VTI 40%, VEA 20%, BND 30%, GLD 10%) grew from $10,000 to $39,418 between Aug 2007 and Oct 2026 (7.4% a year). Its worst fall was -32%, from Oct 2007 to Feb 2009, and it took 38 months (about 3 years) to get back to that high.

Real 2007-08 to 2026-10 data, dividends reinvested, rebalanced yearly. Past performance doesn't predict future results.

Growth of $10,000, Aug 2007 to Oct 2026

Four US stock funds (SPY, VTI, VUG, QQQ, 25% each)A mix across assets (VTI 40%, VEA 20%, BND 30%, GLD 10%)

Run the four US funds with your own numbers →Run the mix across assets with your own numbers →

Keep watching one of them, free: the four US funds or the mix across assets. A free account saves it as your plan and checks it for you every month.

For educational and informational purposes only, not financial, investment, tax, or legal advice. Backtests are hypothetical; past performance does not guarantee future results.