Using Monosnap to find dimensions of available space
I've come across a couple of times during image related trainings where you have to guess the pixel dimensions of a space where you want to insert an image. This involves trial and error - and for newbies more error in the beginning before they get the hang of it. :D
Monosnap (https://monosnap.com/) is a free cloud based screenshot tool. It is easy to learn and use and.... as you are selecting the area you want to capture, it shows you the pixel dimensions as shown in this image:
So when you need to find the dimensions of a space in your sidebar (or wherever) where you want to insert an image, all you have to do is take a screen shot of the available space, and you will know the dimensions you have to work with.
Quite easy and cool!