A typical academic poster will have a three- or four-column layout, with variations of course.
The first example below is a typical academic poster in landscape format (wider than it is high), including a header with three columns. Many landscape format posters have four columns--the format will depend on the requirements for a particular conference and discipline.
The second example below shows an academic poster in portrait format (higher than it is wide).
Be sure to consult the conference or event requirements to see if there are specific rules for formatting posters.
Poster in landscape format: 48" wide x 36" high (121.92 x 91.44 cm)
Poster in portrait format (less common)