Converting CM to Units

Hi community,

I have a 1920 * 1080 screen and I have trouble converting a 7.5 cm circle (H and W) to norm units.

What calculation do I need to make to find the right amount of units?


You can set the units of the circle to cm even if the rest of your experiment is in norm - PsychoPy will handle the conversion for you.

To do the conversion by hand, you need the physical size of the screen. Width in pixels / width in cm gives you the horizontal pixel/cm ratio, then you can do the same with heights to get the vertical ratio. Multiplying the appropriate ratio by the desired number of centimeters gives the necessary number of pixels, which you can then divide by the width or height of the screen in pixels to get the value in norm units.

All that is a bit of a faff, so wherever possible it’s safer to let PsychoPy handle it!

1 Like

Thanks alot! it worked well