How to Measure in Adobe Illustrator

Create or open an object you want to measure. Find the measure tool, it might be temporarily hiding under the eyedropper tool. If the eyedropper tool is showing, you can right click (CTRL + LMB) on the icon and select the measure tool (it will be represented with a ruler).

First click is a start point and stop at the end point. The outcomes are show at the Info box. You can measure your object size in every direction

To measure the space of two object, replete the second step. If you drag your mouse direction from left to right or bottom to top, you will get an outcome with positive number but if you do it in opposite way, you will get a negative number.