Use the Markup Caliper tool to measure the distance between two points on an image.
To measure the distance between points
From the Image area top toolbar, Markup button menu, select Markup Caliper.
Markup Caliper may be the default tool, in which case you do not have to activate it.
Click the start point of the area to measure.
Click the end point.
The distance between the two points is shown between the lines.
To move the measurement text, drag the center control point to a new position.
To change the measurement, drag one of the end control points to a new position.
To set the measurement, right-click.
The measurement values and units used depend on the calibration applied or available to the study. Refer to Understanding measurement values and units used.
To delete the measurement, press the Delete key.