The Financial Times Stock Exchange 100 Index, also called the FTSE 100 Index, is a share index of the 100 companies listed on the London Stock Exchange with the highest market capitalisation. It is seen as a gauge of prosperity for businesses regulated by UK company law. The index is maintained by the FTSE Group, a subsidiary of the London Stock Exchange Group.

Historical Chart

Correlation index and comparison

The FTSE 100 broadly consists of the largest 100 qualifying UK companies by full market value. The total market value of a company is calculated by multiplying the share price of the company by the total number of shares they have issued. Many of these are internationally focused companies, however, so the index’s movements are a fairly weak indicator of how the UK economy is faring and are significantly affected by the exchange rates of the Pound. A better indication of the UK economy is the FTSE 250 Index, as it contains a smaller proportion of international companies.

Even though the FTSE All-Share Index is more comprehensive, the FTSE 100 is by far the most widely used UK stock market indicator. Other related indices are the FTSE 250 Index (which includes the next largest 250 companies after the FTSE 100), the FTSE 350 Index (which is the aggregation of the FTSE 100 and 250), FTSE SmallCap Index and the FTSE Fledgling Index. The FTSE All-Share aggregates the FTSE 100, FTSE 250 and FTSE SmallCap.