Common Poster Sizes
Small: 11×17 Poster Size
11×17 inches is generally the smallest poster size. Anything smaller won’t look like a poster, but instead like a piece of A4 printer paper tacked up on a wall. 11×17 posters are just the right size for indoor notices and event advertisements. They command more attention and look more official than A4-sized flyers but don’t require too much wall space. 11×17 posters are perfect for indoor display in areas where people often congregate, like in lounges, waiting rooms, bathrooms, or near water coolers. 11×17 posters are best placed at eye-level on a wall where people will generally be within a five-foot distance of.
A poster with the dimensions 11×17 inches looks best when printed with designs that use bold typography, simple illustrations, a limited color palette, and lots of negative space. The aspect ratio of 11×17 posters is also similar to the typical movie poster aspect ratio (just short of 2:3), so these poster dimensions can work quite well if you’d like a miniature poster of your favorite film hanging over your desk.
Medium: 18×24 Poster Size
18×24 inches makes for a medium-sized poster that can be displayed both indoors and outdoors. 18×24 is an appropriate and normal poster size for just about any project because it can be appreciated both close up and from a distance. This is also a regular poster size for framing, so you have many display options for 18×24 posters.
18×24 posters look best when displayed on a wall where people will generally be between one and five yards of. For decorative purposes, this average poster size looks great hung behind a reception desk, lining hallways, or in your home. As an advertisement, 18×24 posters are great for public bulletin boards, in-store promotions, college and university campuses, and construction walkways.
18×24 inches is smaller and wider than the standard movie poster size you will find in big box theaters, but it is still a good size for small-scale movie poster printing. Because these poster dimensions are excellent for combining photography and immersive graphics with a few lines of bold text, 18×24 movie posters may work well for advertisements for special screenings or other independently organized film events. Just keep in mind that the aspect ratio for medium posters is 3:4, where official movie posters are designed with an aspect ratio closer to 2:3.
Large: 24×36 Poster Size
24×36 inches are the dimensions in which large format posters are most often printed. If you were to go into a store that specifically sold posters, chances are a large portion of their inventory would be 24×36 posters. You will find many options for framing posters that measure 24×36, and with an aspect ratio of 2:3, many images (including movie posters) fit nicely at these dimensions.
24×36 posters are the classic choice for posters that need to stand out in a crowd. For busy malls, side walk advertisements, trade shows, festivals, and other locations with high foot traffic, this is a standard poster size that can be seen from a distance. Depending on the design, they are large enough to be legible from up to ten yards away. 24×36 posters look best when the center point of the poster is at eye-level. 
