“Do Not Disturb” door hangers, commonly used in hotels and other accommodation settings, typically adhere to a standard size that balances visibility and practicality. The most common size for these door hangers is approximately 3.5 inches wide by 8.5 inches tall (about 9 cm by 21.5 cm). This size is large enough to be noticeable and provide sufficient space for the “Do Not Disturb” message or any additional information, such as branding for a hotel, while also fitting comfortably on most doorknobs without being cumbersome.

Some variations exist, with slight adjustments in dimensions or shape based on the preference of the hotel or manufacturer, but the 3.5 x 8.5 inches size is generally the industry standard. The design often includes a hole or a slit at the top, allowing it to easily slide over or hang from a doorknob, and the material is usually durable to withstand handling and environmental factors like humidity.