It is tempting to think that more funds automatically means more diversification, and more diversification automatically means less risk. In practice, many UK investors end up holding a dozen or more funds that overlap heavily in their underlying holdings, creating the illusion of a well-spread portfolio while adding complexity, cost and confusion without any real reduction in risk. Understanding how many funds are actually needed — and why the number is usually smaller than people assume — is one of the more counter-intuitive but valuable lessons in portfolio construction.
Why diversification has diminishing returns
Diversification works by combining assets whose returns do not move perfectly in step with one another, so that the ups and downs of individual holdings smooth out at the portfolio level. This effect is powerful at first: moving from one fund to a handful of genuinely different funds meaningfully reduces the impact of any single holding performing badly. But the marginal benefit falls quickly. Once a portfolio already holds broad exposure to global equities across regions, sectors and company sizes, adding an eleventh or twelfth fund typically adds very little extra diversification — because those funds increasingly hold many of the same underlying companies.
The mathematics in plain terms
A single global equity tracker fund can already hold several thousand individual companies across dozens of countries. Adding five more regional or sector funds on top does not multiply that diversification five-fold; it mostly re-slices exposure to companies already represented, while adding five extra sets of charges, five extra sets of paperwork, and five extra things to monitor.
Signs of over-diversification
- Fund overlap — several funds independently hold large positions in the same handful of mega-cap companies, so the portfolio's true concentration is higher than the number of funds suggests.
- Return convergence — the portfolio's overall behaviour ends up looking almost identical to a single broad index, but at a higher blended cost.
- Difficulty explaining the portfolio — if an investor cannot say in a sentence or two what role each fund plays, that is often a sign the fund is redundant rather than additive.
- Administrative drag — more funds means more factsheets to read, more rebalancing decisions, and more chances for a fund to be quietly forgotten and left unreviewed for years.
How many funds is typically "enough"
There is no single magic number, and the right answer depends on the building blocks used, but some broad reference points are commonly discussed among portfolio commentators:
| Approach | Typical number of funds | Notes |
|---|---|---|
| Single-fund solution | 1 | A multi-asset or "all-in-one" fund covering equities and bonds globally. |
| Simple core portfolio | 2–4 | E.g. a global equity tracker plus a bond fund, perhaps split by region. |
| Core-and-satellite | 4–8 | A core holding plus a small number of targeted satellite positions. |
| Highly diversified, hands-on | 8–15 | Requires active monitoring to avoid unintentional overlap and cost creep. |
Beyond roughly 15–20 holdings, many commentators argue a private investor's portfolio starts to behave less like a deliberately diversified strategy and more like an unmanaged collection of past decisions.
Why more funds can accumulate over time
Historical decisions never revisited
Many over-diversified portfolios were not built that way deliberately. They accumulate gradually — a fund bought on a recommendation five years ago, another added after reading about a promising sector, a legacy holding from before an investor understood index funds — none of which is ever removed, simply added to.
A false sense of safety
Holding many funds can feel prudent, as though spreading money across more decisions must reduce risk. But if those funds are highly correlated — for example, several different UK equity income funds that all hold similar large-cap dividend payers — the portfolio may be far less diversified than it appears, while carrying more total cost.
The cost side of holding too many funds
Each additional fund carries its own ongoing charges figure, and a portfolio's overall blended cost is simply the weighted average of every holding's individual charge. Adding funds without a clear purpose does not just risk diluting genuine diversification — it can also quietly raise the total cost of the portfolio, since specialist or actively managed satellite-style funds are frequently more expensive than a broad low-cost tracker. Over long holding periods, even a modest increase in blended cost, spread across many redundant holdings, can compound into a meaningful drag on total returns, in much the same way that a single high-cost fund would.
An illustrative comparison
| Portfolio structure | Illustrative blended ongoing charge | Genuine diversification benefit |
|---|---|---|
| One global tracker fund | Around 0.15–0.25% | Broad, already covers thousands of companies |
| Nine overlapping funds, several duplicating similar large-cap exposure | Often 0.50–0.90% or more, blended | Limited additional benefit over the single tracker |
These figures are illustrative only, intended to show the general pattern rather than to describe any specific real fund or portfolio.
A practical approach to rationalising a portfolio
- List every fund held, along with its stated objective and its top ten holdings, available on the fund factsheet or provider's fund page.
- Identify overlapping holdings — companies or sectors that appear across multiple funds.
- For each fund, ask what specific role it plays that is not already covered elsewhere.
- Where two funds serve essentially the same role, consider consolidating into the lower-cost or more broadly diversified of the two.
- Reassess the resulting number of funds against the portfolio's overall complexity tolerance — some investors are comfortable monitoring more moving parts than others.
A worked example
Suppose a hypothetical investor holds nine funds in a £60,000 ISA: three separate UK equity funds, two global equity funds, two emerging markets funds, a UK smaller companies fund and a global technology fund. On reviewing the underlying holdings, they find that the three UK equity funds all hold very similar sets of large FTSE 100 companies, and that the technology fund's top holdings substantially duplicate positions already present in both global equity funds. Consolidating the three UK funds into one, and the two global funds into one, while keeping a single emerging markets fund and the smaller companies fund, could reduce the portfolio from nine holdings to perhaps four or five — likely lowering the blended cost, simplifying rebalancing, and, in many cases, not meaningfully reducing genuine diversification at all, since much of the apparent variety was illusory.
When holding more funds does make sense
None of this means fewer funds is always better in every circumstance. Additional funds can be genuinely justified when they provide access to an asset class the core does not cover at all — such as a dedicated bond fund, a property fund, or a specific regional exposure meaningfully under-represented in a global index. The test is not the number itself, but whether each fund adds something distinct.
Legitimate reasons the count might grow
- Spreading holdings across an ISA, a SIPP and a general investment account for tax reasons can mean similar-sounding funds appear more than once across a portfolio, even where the underlying strategy is not genuinely duplicated at the account level.
- Splitting a single asset class into more targeted building blocks — for example, separate developed-market and emerging-market equity funds instead of one combined global fund — can be a deliberate choice to control the weighting between them more precisely, rather than uncontrolled fund accumulation.
- Introducing a new asset class, such as adding a first bond fund to a previously all-equity portfolio as retirement approaches, is a genuine addition rather than redundant overlap.
How platform tools can help spot overlap
Several UK investment platforms and independent research tools offer "portfolio X-ray" style features, which look through the underlying holdings of every fund in a portfolio and aggregate them into a single combined view — showing, for example, the true combined weighting to any individual company, sector or country across all funds held. These tools can reveal overlap that is not obvious from fund names alone, and are worth using periodically, particularly for portfolios that have grown gradually over many years without a single, deliberate design.
What to look for in an aggregated view
- Whether any single company represents an unexpectedly large share of the total portfolio once all funds are combined.
- Whether the combined sector or regional weightings look sensible, or whether one area is inadvertently dominant.
- Whether the combined asset allocation (equities, bonds, cash, and any alternatives) matches the investor's intended overall risk level, once looked at as a whole rather than fund by fund.
A note on cost when consolidating
When consolidating overlapping funds, it is worth checking whether selling and repurchasing within an ISA or SIPP incurs any dealing charges on the platform used, and, for holdings outside a tax wrapper, whether the sale would trigger a taxable gain. Consolidation is usually still worthwhile even where a modest cost applies, given the ongoing savings from simplified monitoring and typically lower blended fees, but it is a factor worth checking rather than assuming to be free in every case.
A final sanity check
If in doubt about whether a portfolio has grown too complex, a simple test is to imagine explaining the portfolio to someone else from scratch. If that explanation runs to a long list of individually justified holdings with overlapping rationales, it is often a sign that consolidation, rather than further addition, is the more useful next step.
Key takeaways
- Diversification benefits fall away quickly once a portfolio already has broad global exposure — extra funds often add cost without meaningfully reducing risk.
- Fund overlap — several funds holding the same underlying companies — is a common but easy-to-miss problem.
- Many hands-off portfolios can be built with as few as one to four funds; more complex approaches rarely need more than eight to ten.
- A useful test for any fund is whether you can state, in one sentence, the distinct role it plays.
- Periodically reviewing underlying holdings, not just fund names, helps reveal hidden overlap.
- Always check current HMRC and FCA figures and allowances, as these change from tax year to tax year.