The idea is great especially the popup scale.

Issues I faced: I use 27" Qhd monitor at 125% scale. The ruler showed 48cm width intially but when I shifted to 100% scale it became 60cm. If I shift to FHD, it goes to 36cm. I thought an actual size ruler will maintain width. Let me know if I am not using it correctly.

I will fix it, thanks to all feedback