[djoldman]

Not to support or attack the rationale behind the css or html standards but these have exact real world SI unit meanings:

   CSS  |                    | Exact Size | Exact Size    
   Unit | Name               | (Inches)   | (Millimeters) 
  --------------------------------------------------------
   cm   | Centimeter         | 50/127     | 10            
   mm   | Millimeter         | 5/127      | 1             
   Q    | Quarter-millimeter | 5/508      | 1/4           
   in   | Inch               | 1          | 127/5         
   pc   | Pica               | 1/6        | 127/30        
   pt   | Point              | 1/72       | 127/360       
   px   | Pixel              | 1/96       | 127/480                 

https://en.wikipedia.org/wiki/Inch

https://en.wikipedia.org/wiki/Millimetre

https://www.w3.org/TR/css-values-3/#absolute-lengths

[dylan604]

Never heard of the Quarter-millimeter before. Strange mix of divisions by tens suddenly switching to divisions of twos

[stevesimmons]

I'd never heard of it either. A comment further down suggests it is Japanese.

Digging deeper, the kyu -- or Q for quarter millimeter -- is apparently a foundational distance measurement in Japanese typesetting, which is metric and operates on a millimeter grid.

[twic]

The article mentions:

> the German and Japanese point is 0.250 mm

It's probably the sanest adaptation of the point to the metric system. A traditional point is close to a third of a millimetre, but that's too weird.

Since the Q is close to 3/4 of a traditional point, it's also quite easy to convert from traditional multiple-of-three point sizes: 9 pt -> 12 Q, 12 pt -> 16 Q, etc.

Although it's even easier just to call those 3 mm and 4 mm!

[m463]

When the mcdonalds quarter pounder with cheese came out, the europeans came out with this government sponsored measurement for fast food chains to standardize and compete without adopting american standards. (like usb-c over lightning)

;)

[WillAdams]

It's known as the _kyu_ in Japan and used for specifying type (font) sizes.