how do you measure an area to put a fan. i am looking to buy a fan for an empty space i have on my computer. the grill and place to put screws is already there and i meassured it with a mm ruler and i get 9mmx9mm
but i go to a site to buy a fan and they have demensions of 40x10mm and 60x25mm and measurements like that. anyone know what i am doing wrong???

since all fans have the shape of the square, there's no need to display hight and length at the same time, so when the site displays 80mmx25mm means actualy 80x80x25 where 25 is the depth of the fan/how fat it is

yeah but i measured 9mm top to bottom all thier measurements are above 60mm is my ruler wrong or something

i would say u r lookin at the cm side of your ruler unless u want a fan smaller then a keyboard key, i think u would need a 90mm fan