Looking for a screen measuring app for macOS I need an app to be able to measure distances at the very least that would correspond to real values. Let's say I have a graphic that has a few points on it instead of having to print out the paper and measure the distances between points by ruler, I'd like to do it on screen. 

Could you suggest the best on screening measuring tool that there is? If it would come with other tools it would be really great.
Cmd-shift-4 brings up a screen capture utility. As you move the new cursor it displays the number of pixels you move in x and y directions. So you can easily measure pixel distance between 2 points. You don't have to capture the screen area, just opt out of that option.

I've also used the app PixelStick ($7 but free trial) that brings up a screen measuring tool. It lists current pixel, the distance between pixels, and the angle between two pixels. You can calibrate the pixel distance to other scales and has a built in map mode. It also has a screen capture button and a color grabber.