The Measure tool calculates the distance between any two points in the document window. When you measure from one point to another, the distance measured is displayed in the Info panel. All measurements except the angle are calculated in the units of measure currently set for the document.
After you use the Measure tool to measure an item, the line or lines remain visible until you take another measurement or select a different tool.
The width and height measurements appear in the Info panel.
To measure an angle from the x axis, drag the tool.
To measure a custom angle, drag to create the first line of the angle. Position the tool over either end point of the measure line. To create the second line of the angle, either double-click and drag, or press Alt (Windows) or Option (Mac OS) and drag.
When you measure a custom angle, the Info panel shows the length of the first line as D1 and the length of the second line as D2.