Online pixel density calculator

If, like me, you have a love-hate relationship with pixels, you might find use for the DPI/PPI Calculator next time you're looking for a new monitor. It calculates the pixel density of any display from its dimensions and resolution without the fuss of doing any mental math. (It informed me that those giant 42" 4k monitors will actually have rather chunky pixels--108 ppi--and are not what I'm looking for.)