The length from the nasal opening to the nasopharynx is typically 8-10 cm in adults and shortens accordingly with age in children.
The vertical extent of the nasal opening to the nasopharynx includes the nasal vestibule, the intrinsic nasal cavity, and the nasopharyngeal cavity, which is typically 8-10 cm long. The nasal vestibule is a cavity surrounded by a ring of skin tissue, the measurement of the longitudinal axis of the intrinsic nasal cavity should pass through the common nasal passages parallel to the base of the nose, and the dome-like cavity that communicates with the nasal cavity anterior to the upper part of the pharynx is the nasopharynx. The three are added together perpendicular to the cervical vertebrae i.e. the length from the nasal opening to the nasopharynx.
From birth to adulthood, the length from the nasal opening to the nasopharynx gradually increases. If there is no interference from adenoid hypertrophy, deviated septum, nasal polyps, etc., the nasal swabs can be successfully probed, otherwise the total length will be lower than this average distance.
If you still have questions, please consult an ENT specialist.