F-number (disambiguation)

The f-number is the ratio of the lens's focal length to the diameter of the entrance pupil.

F-number or F number also may refer to:

• F number (chemistry), is a number that can be calculated for polycyclic aromatic hydrocarbons from their structure

• F-ratio (disambiguation)
• F scale (disambiguation)
• F1 (disambiguation)
  • a filial number or filial generation number, such as in the case of F1 hybrids, or F₂, F₃, etc.
  • Fujita scale, a rating of a tornado's intensity by its impact on structures and vegetation
  • function keys (on a computer keyboard, F1, F2, F3, etc.)
• F2 (disambiguation)
• F3 (disambiguation)
• F15 (disambiguation)
• F150 (disambiguation)