I needed an accurate measurement but my calipers only measure 155 mm at it's max.
I actually run into this often, so I decided to make a little measuring stick. The minor tick marks are 2 mm each and major are 10 mm as counted off by the numbers. Most measuring sticks that go to this length are in cm vs mm. This might make it a bit non standard, but everyone that I know that designs "things" just type in mm. Well at least I do!.

This is printed using a .2 mm nozzle. IT WILL NOT WORK with .4 mm nozzle because the slicer will not create the numbers. Nozzles of .3 and a .25 mm do slice correctly but if you have a .2 mm, you will be MUCH happier with the results!
Measuring with my digital calipers, the 154 mm spot on the ruler was EXACTLY 154.00 mm.

As for the black numbers, I printed this ruler exclusively in white Ziro PLA. I then used a magnifying glass and a "fine point" sharpie to highlight the numbers. The numbers are raised enough that it was not even a hard task to get just the numbers and not mess it up.
A larger or blunter sharpie would still work just as well because of the clearance difference between the numbers and the ruler base.

Giving back to the community, enjoy!

Thinking of making a longer one but I started with one that I know most of the people with standard sized beds are at about 250 mm max bed sizes. Don't forget that if your in the 220 mm area, you can move to a diagonal (corner to corner) print direction to get a longer max being that this item is small. Any shorter than 150 mm, you might just as well use your calipers.