In stock-market investing, what does the Nikkei 225 index track?

In stock-market investing, the Nikkei 225 index tracks 225 companies listed on Japanese stock exchanges.

It is Japan’s best-known stock index and is calculated by Nikkei Inc. The index is price-weighted, meaning a constituent’s influence depends primarily on its share price after adjustment, rather than directly on its total market capitalization. This differs from many major indexes that use market-capitalization weighting.

The Nikkei 225 began on 7 September 1950, although its historical calculation was later extended back to 1949. Its constituents represent prominent Japanese companies across industries such as manufacturing, technology, retail, finance, and transportation. The list is reviewed periodically.

The index is often called the Nikkei or Nikkei Stock Average. It should not be confused with the broader TOPIX index, which covers a wider set of companies on the Tokyo Stock Exchange and uses a different weighting approach.