Guides / FTSE 100 vs FTSE 250: how the two indices differ and how to read the comparison
FTSE 100 vs FTSE 250: how the two indices differ and how to read the comparison
The FTSE 100 is the 100 largest eligible UK companies by full market capitalisation, and the FTSE 250 is the next 250. A quarterly review moves companies between them, using buffers so firms near the line do not switch every quarter. Neither index is the better one. They measure different slices of the same market.
Short answer: both indices are cut from one ranked list of UK companies. The top 100 make up the FTSE 100, and the next 250 make up the FTSE 250. Everything else on this page follows from that list: how it is ranked, how often it is checked and what happens to a company near the boundary.
For a full profile of each index on its own, see what is the FTSE 100 index and what is the FTSE 250 index. This page puts the two side by side.
How companies are placed: size bands and market capitalisation
The FTSE UK Index Series Ground Rules, published by FTSE Russell, define both indices:
- FTSE 100: "the largest 100 UK companies by full market capitalisation" that qualify for inclusion.
- FTSE 250: "the next 250 UK companies ranked by full market capitalisation" outside the FTSE 100.
Two words in those definitions matter.
Full market capitalisation means the ranking uses a company's whole value, "before the application of any investability weightings". Free float, the share of a company's stock available to ordinary investors, comes in later. It affects how much weight a company has inside the index, not where it ranks.
Qualify means a company has to pass FTSE Russell's tests before it is ranked at all. The Ground Rules require shares admitted to the Main Market of the London Stock Exchange, a minimum free float of 10%, a liquidity test and UK nationality as FTSE Russell defines it. That last test is more involved than where a company happens to be listed. So the ranked list is not every company quoted in London, sorted by size.
Where the FTSE 350 fits
The FTSE 350 is the FTSE 100 and FTSE 250 combined. The Ground Rules say it represents "the largest 350 companies included in the FTSE UK Index Series". A company that moves between the FTSE 100 and the FTSE 250 stays inside the FTSE 350 the whole time.
The FTSE SmallCap sits below the FTSE 350. The FTSE All-Share is the FTSE 350 and the SmallCap together. On LSEG's index page, the FTSE 250 is described as representing about 15% of UK market capitalisation.
Quarterly reviews: how a company moves between the FTSE 100 and FTSE 250
Under the Ground Rules, the series is reviewed every quarter, in March, June, September and December. The review works like this:
- The ranking uses data on the FTSE UK Monitored List at the end of the day on the Tuesday before the first Friday of the review month.
- Every eligible company is ranked by full market capitalisation, largest first.
- The buffer rules below decide who joins and who leaves.
- Changes take effect after the close on the third Friday of the review month, so the new line-up starts trading on the Monday.
The buffers are where the detail lies. Taken from the Ground Rules:
- A company joins the FTSE 100 if it has risen to 90th or above.
- A company leaves the FTSE 100 if it has fallen to 111th or below.
- A company joins the FTSE 250 if it has risen to 325th or above.
- A company leaves the FTSE 250 if it has fallen to 376th or below.
That creates a band between 91st and 110th where a company normally stays wherever it already is. A FTSE 250 company ranked 95th does not move up, and a FTSE 100 company ranked 105th does not drop. FTSE Russell says the rules are "designed to provide stability" while still catching companies that have "risen or fallen significantly". Companies that leave the FTSE 100 normally go into the FTSE 250, and companies that join the FTSE 100 leave the FTSE 250.
What a move means
Promotion or relegation tells you about a company's size compared with other companies on one cut-off date. It does not judge the business. Because the rank is relative, a company can move up because others shrank, or move down because others grew. Its own value may have changed very little.
What the two indices are made of: sector mix and overseas earnings
The FTSE Russell factsheets break each index down by industry using the Industry Classification Benchmark (ICB). On the FTSE 250 factsheet dated 30 September 2026, financials was the largest industry by weight, at about 42%. That group includes many investment trusts. Industrials and consumer discretionary came next. These weights change every month, so check the date on any factsheet you read.
A reading tip: the same FTSE 250 factsheet gives the number of constituents as 251. The Ground Rules count companies, but factsheets count share lines, and the rules allow a company to have a secondary share line in the index as well.
On overseas earnings, no FTSE Russell or LSEG source we checked gives a revenue split for either index, so this page does not quote one. The general point still helps. Many of the largest UK-listed companies are multinational groups, so their results depend on events far beyond the UK. Mid-sized companies are more mixed. To see where a particular company earns its money, read its annual report rather than an article's summary.
How to read a FTSE 100 v FTSE 250 comparison without over-reading it
A comparison chart or factsheet describes the past. It does not forecast the future. A few checks help:
- Price or total return? FTSE Russell publishes price indices and total return versions that reinvest dividends. The two can show quite different pictures over long periods.
- Start date. The FTSE 250 factsheet rebases every line to 100 at the start of its ten-year window. Choose a different start date and the gap between the lines changes.
- Constituents change. Each quarterly review alters the membership, so a ten-year line is not following the same set of companies.
- Weights. A few large companies can dominate an index's movements, which is why an industry table matters as much as the headline line.
For the same habits applied to one index over decades, see how to read a long-term FTSE 100 chart.
Why past performance gaps do not tell you what happens next
Say one index beat the other over five years. That tells you what happened to those companies during that period, and nothing about what comes next. The FCA's conduct rules (COBS 4.6) require firms that show past performance of an investment or a financial index to include a prominent warning that "past performance is not a reliable indicator of future results". The same applies to any chart you read.
That is why this page quotes no returns figures. The structural differences above explain why the two indices can move apart. They do not tell you which one will lead next.
Where to read the official rules and constituent lists
Go to the primary source:
- The FTSE UK Index Series Ground Rules set out eligibility, the definitions and the review buffers.
- The LSEG UK indices page links to each index's factsheet and to its adds and deletes after each review.
- The factsheets give the industry breakdown and the largest constituents as at the date printed on them.
Lists of constituents go out of date after every review. For why that happens and how to check that a list is current, see where to find the FTSE 250 list of companies.
Reading company news for each tier on MarketFrame
MarketFrame covers FTSE 100 companies only. It does not cover FTSE 250 company news.
For the FTSE 100, the daily hub is at FTSE news, and each company's and sector's history is in FTSE news analysis. Each company gets a tone score from −10 (clearly bad news for the company) to +10 (clearly good). It measures the tone of news coverage. It is not a share-price forecast and should not be used as one. The archive starts on 30 September 2026.
Questions
What is the difference between the FTSE 100 and the FTSE 250?
The FTSE 100 is the largest 100 eligible UK companies ranked by full market capitalisation. The FTSE 250 is the next 250. Both come from the same ranked list, so the main difference is company size, and the different mix of industries that follows from it.
What is the FTSE 350?
The FTSE 100 and FTSE 250 combined, which makes it the largest 350 companies in the FTSE UK Index Series.
How does a company move from the FTSE 250 to the FTSE 100?
At a quarterly review, held in March, June, September or December. A company joins the FTSE 100 if it has risen to 90th or higher. A FTSE 100 company leaves if it has fallen to 111th or lower.
Why do the FTSE 100 and FTSE 250 move differently?
They hold different companies with a different industry mix, so the same news affects each one differently. That does not tell you which one will do better next.
Where can I find the official list of companies in each index?
On FTSE Russell's LSEG index pages, which publish the factsheets and the changes made at each review. Check the date on any list, because membership changes every quarter.
Questions people ask
What is the difference between the FTSE 100 and the FTSE 250?
The FTSE 100 is the largest 100 eligible UK companies ranked by full market capitalisation. The FTSE 250 is the next 250 companies below them. Both come from the same ranked list, so the main difference is company size, and the different mix of industries that follows from it.
What is the FTSE 350?
The FTSE 350 is the FTSE 100 and the FTSE 250 combined. FTSE Russell's Ground Rules describe it as the largest 350 companies in the FTSE UK Index Series.
How does a company move from the FTSE 250 to the FTSE 100?
It moves at a quarterly review, held in March, June, September and December. A company joins the FTSE 100 if it has risen to 90th place or higher in the ranking. A FTSE 100 company leaves if it has fallen to 111th or lower. Companies ranked in between normally keep their current index.
Why do the FTSE 100 and FTSE 250 move differently?
They hold different companies with a different industry mix, so the same news affects each one differently. That explains why the two indices can diverge. It does not tell you which one will do better next.
Where can I find the official list of companies in each index?
FTSE Russell publishes constituent lists, factsheets and the adds and deletes from each review on its LSEG index pages. These lists change after every quarterly review, so check the date on any list you read.