If you follow the UK stock market, you have probably heard the FTSE 100 mentioned whenever financial markets make the news. The FTSE 250 receives less attention, but it represents another important part of the London-listed market.

At first glance, the FTSE 100 versus FTSE 250 comparison seems straightforward. One tracks 100 large companies, while the other contains 250 somewhat smaller businesses.

But the real differences go much deeper.

The two indices can have very different exposure to the UK economy, international markets, industries, currencies, and economic cycles.

FTSE 100 companies include many large multinational businesses earning much of their revenue overseas, while companies in the FTSE 250 tend to have greater exposure to domestic UK activity.

FTSE Russell describes the FTSE 100 as 100 highly capitalised blue-chip companies listed on the London Stock Exchange, while the FTSE 250 contains mid-cap companies outside the FTSE 100 and represents approximately 15% of UK market capitalisation.

Understanding those differences can help investors interpret UK market movements more intelligently.

1. What Is the FTSE 100?

The FTSE 100 is one of the best-known stock market indices in Europe.

In simple terms, it tracks 100 of the largest eligible companies listed on the London Stock Exchange based primarily on market capitalisation and the index’s eligibility requirements.

Market capitalisation means the market value of a company’s shares. FTSE Russell uses market-cap weighting, so larger companies have a greater influence on index movements than smaller constituents.

Imagine Company A represents 7% of the index while Company B represents just 0.5%.

A major price movement in Company A would have a much greater impact on the FTSE 100’s overall performance.

The index therefore does not give every company an equal vote.

Large multinational businesses in industries such as banking, energy, pharmaceuticals, consumer goods, mining, and industrials can have considerable influence over the index.

That global exposure is one reason the FTSE 100 should not automatically be treated as a pure measurement of the British economy.

2. What Is the FTSE 250?

The FTSE 250 sits immediately below the FTSE 100.

FTSE Russell describes it as an index of mid-capitalised companies that are not included in the FTSE 100. Together, the two indices form the FTSE 350.

A simple way to visualise the structure is to imagine eligible London-listed companies arranged from largest to smallest.

The biggest group forms the FTSE 100. Broadly speaking, the next 250 companies make up the FTSE 250, subject to the index methodology and eligibility requirements.

That means the FTSE 250 contains smaller businesses than the FTSE 100, but “smaller” is relative.

Many are still substantial public companies with established operations, thousands of employees, and significant revenues.

The FTSE 250 also includes some investment trusts large enough to qualify for index membership. Fidelity notes that it tends to contain companies with greater reliance on domestic operations than the larger businesses found in the FTSE 100.

3. The Biggest Difference Is Company Size

The most obvious diference between the two indices is market capitalisation.

FTSE 100 constituents sit at the large-cap end of the UK-listed market, while FTSE 250 companies broadly represent the next tier.

This matters because company size can influence investment characteristics.

Large multinational corporations often have diversified operations, established brands, greater access to capital, and businesses spread across multiple countries.

Mid-sized businesses can have greater room for expansion, but they may also be more sensitive to financing conditions and economic changes.

Do not assume that membership is permanent, however.

FTSE Russell reviews the UK indices regularly. Under its review rules, companies can move between the FTSE 100 and FTSE 250 when their market values change enough to cross specified ranking thresholds.

For example, the September 2026 review promoted easyJet and Ithaca Energy into the FTSE 100, while Entain and Persimmon moved in the opposite direction.

The indices therefore evolve alongside the market.

4. FTSE 100 Companies Are More International

Here is where the comparision becomes more interesting.

A company being listed in London does not mean most of its customers are British.

Many FTSE 100 companies operate globally, earning revenue from North America, Europe, Asia, emerging markets, and other regions.

Recent analysis citing LSEG data found that more than four-fifths of FTSE 100 company sales were generated outside the UK. The equivalent overseas figure for the FTSE 250 was around 55%, highlighting its relatively stronger domestic exposure.

That difference has practical consequences.

If the British economy slows while global economic conditions remain relatively strong, multinational FTSE 100 businesses may be less dependent on UK consumer spending.

The FTSE 250 can be more sensitive to conditions closer to home.

Interest rates, housing activity, consumer confidence, employment, business investment, and UK economic growth can therefore play a larger role in the fortunes of many mid-cap companies.

This is why the FTSE 250 is sometimes described as a more domestically focused barometer of UK business conditions.

5. Currency Movements Can Affect Them Differently

International exposure introduces another variable: currencies.

Imagine a FTSE 100 company earns billions of dollars from overseas operations but reports its financial results in pounds.

If sterling weakens against the dollar, those overseas earnings may translate into more pounds when reported back in the UK.

That does not mean a weaker pound automatically sends the FTSE 100 higher. Businesses face many other factors, including costs, debt, commodity prices, demand, and currency hedging.

But the principle explains why movements in sterling can matter to internationally focused UK-listed companies.

The FTSE 250’s greater domestic exposure can make the effect somewhat different.

Because a larger proportion of activity occurs within Britain, local interest rates and economic conditions may sometimes matter more than currency translation.

Again, these are broad index characteristics rather than rules that apply identically to every company.

6. Does the FTSE 250 Offer More Growth Potential?

Mid-cap companies are sometimes associated with stronger growth potential because they have more room to expand than enormous multinational corporations.

A £3 billion business doubling in size is generally easier to imagine than a £150 billion company doing the same thing.

But potential growth does not come free.

Smaller and mid-sized companies can experience greater volatilty. They may have less diversified operations, weaker access to finance, or greater dependence on particular markets.

Hargreaves Lansdown has noted that historically the FTSE 250 can experience a bumpier ride than the FTSE 100, reflecting both company size and its greater sensitivity to the UK economy.

Investors should therefore avoid assuming that the FTSE 250 is simply the “higher-return version” of the FTSE 100.

There will be periods when large caps perform better and periods when mid-caps lead.

Economic conditions, valuations, interest rates, sector performance, and investor sentiment can all change the result.

Past performance also cannot guarantee future returns.

7. Sector Exposure Is Different Too

Company size is not the only thing separating these indices.

Their sector composition can differ substantially.

The FTSE 100 has historically contained significant exposure to areas such as financials, energy, healthcare, consumer staples, and multinational industrial businesses.

The FTSE 250 contains a broader collection of mid-cap businesses and investment trusts, with different weights across financials, industrial companies, consumer businesses, real estate, technology, and other areas.

These differences can help explain why the indices sometimes move in opposite directions on the same day.

For example, rising oil prices might support large energy companies that carry meaningful weight in the FTSE 100 while having much less direct influence on many FTSE 250 constituents.

Meanwhile, improving UK consumer confidence could benefit domestic retailers, leisure businesses, property companies, or other mid-cap stocks.

Investors are therefore buying different economic exposures even though both indices belong to the UK-listed market.

8. FTSE 100 Versus FTSE 250 for Income Investors

Dividends are another factor worth considering.

The FTSE 100 has traditionally contained many mature companies that return cash to shareholders through dividends. Large banks, energy businesses, insurers, consumer groups, and other established companies can make the index attractive to income-focused investors.

That does not mean every FTSE 100 company pays a generous dividend, or that dividends are guaranteed.

Companies can reduce or suspend distributions when profits or cash flows weaken.

The FTSE 250 also contains dividend-paying companies, but the balance between growth and income can differ.

Some mid-cap businesses may prefer reinvesting a larger proportion of earnings into expansion.

Investors comparing the two should therefore look at total return rather than dividend yield alone.

Total return considers both share-price movements and income received from investments.

9. Can Investors Hold Both?

There is no requirement to choose one index and ignore the other.

An investor seeking broader exposure to large and mid-sized London-listed companies could potentially hold investments covering both.

In fact, that combination already has its own benchmark.

The FTSE 350 combines the FTSE 100 and FTSE 250, representing large- and mid-cap stocks that meet FTSE Russell’s relevant criteria.

Go even broader and the FTSE All-Share combines the FTSE 100, FTSE 250, and FTSE SmallCap indices. FTSE Russell says it represents around 98–99% of UK market capitalisation.

The appropriate exposure depends on an investor’s goals.

Someone wanting more multinational large-cap exposure might lean differently from an investor seeking greater sensitivity to British economic activity.

Neither approach removes investment risk.

Diversifying across company sizes, industries, and geographic markets can help reduce concentration, but share prices can still fall significantly.

The FTSE 100 versus FTSE 250 debate is really about much more than 100 companies versus 250.

The FTSE 100 contains the largest eligible London-listed companies and has significant international business exposure. The FTSE 250 represents the next tier of mid-cap companies and generally has a stronger connection to the domestic UK economy.

That creates different sensitivities to currencies, economic growth, interest rates, sectors, and market sentiment.

Neither index is automatically better. They simply provide different types of market exposure.

Before investing, look beyond the index name and consider what you actually want your portfolio to contain. Compare company size, geographic exposure, costs, diversification, and risk, then decide how UK equities fit within your broader long-term investment strategy.