I couldn't find the exact pixel dimensions for this calculator, so I just measured it myself.
1 Centimeter = 22 Pixels, exactly.
Edit: It might not appear in the photo to be an exact alignment with centimeters, but that's all because of the ruler sitting a little higher than the screen and the camera optical focus and crap.
Indeed, it's exactly 22px/cm
You cut and grind your ruler?
I use the little machinist rulers that are edge ground but only 150mm most of the time. I hate my 460mm Westcott ruler because of the 3.75mm inset zero position but never bothered to cut it.
No. The ruler is a machinist's grade Staedtler MARS 963 53-12.
It was manufactured that way, for precision.