National standards stipulate that mirror dimensions vary by vehicle model. Exterior rearview mirrors range from 18 to 35 cm in width, while interior rearview mirrors range from 9 to 12 cm in width.
Minimum dimensions for interior rearview mirrors (Class I)
It must be possible to inscribe a rectangle on the reflecting surface with a height of 40 mm and a base length of *a*.
Minimum dimensions for exterior rearview mirrors (Classes II and III)
It must be possible to inscribe a rectangle on the reflecting surface with a height of 40 mm and a base length of *a*, as well as a line segment of length *b* parallel to the height of that rectangle.
1. Compact cars: Width 18–25 cm, height 25–35 cm (e.g., Honda Fit); designed to ensure maneuverability.
2. Mid-size cars: Width 22–30 cm, height 30–40 cm (e.g., VW Magotan/Passat); provides a wider rear field of view.
3. Large SUVs/MPVs: Width 28–35 cm, height 35–45 cm (e.g., Toyota Highlander); helps minimize blind spots caused by the A-pillar.
4. Mirror glass details: The glass itself is typically slightly smaller than the housing; for instance, the mirror glass on an Audi A7 measures approximately 15–20 cm in length and 8–12 cm in width.