The Dow Jones Industrial Average’s largest one-day percentage gain was 15.34%, recorded on March 15, 1933.
The rise came during a dramatic period in the Great Depression. President Franklin D. Roosevelt had declared a national banking holiday earlier that month, temporarily closing banks while authorities sought to restore confidence in the financial system. Reopening banks and emergency measures helped improve sentiment.
On March 15, trading resumed with powerful buying, and the Dow gained 8.26 points, or 15.34%, to close at 62.10. The percentage was enormous because the index level was very low compared with modern values.
This record is often confused with the biggest point gain, which has occurred many times in later decades as the Dow’s numerical level became much higher. Percentage records and point records measure different things.