H number or H-number may refer to:

• H-number (photography), an aperture setting used on Rodenstock Tiefenbildner Imagon lenses
• H number (musical catalogue), a number associated with musical catalogues by Harry Halbreich
• h-index, an index that attempts to measure productivity and citation impact of the published body of work of a scientist or scholar
• Herfindahl index, a measure of size of firms in relation to the industry and an indicator of the amount of competition among them

This disambiguation page lists articles associated with the title H number.
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