I agree with this. You should have exactly 6" between 12 pins on the chain. Your 6" end on the ruler is lined up pretty good on one pin, but the 12th pin, counting down the ruler, falls way off the end of the ruler. It should line up exactly with the 0" end of your ruler. You can see by 3" or even 4" on your ruler, your pins are not exactly in line with the mark. Unless I'm interpreting your photograph incorrectly, I'd say that chain is significantly worn.

Edit: you normally measure 24 pins across 12" to get a more accurate measurement of chain wear. You can see (again, if I'm interpreting your photo correctly) significant wear across only 6". It looks like 12 of your chain pins measure about 6-1/16" or so (or maybe even 6-1/8"). 24 pins would probably measure between 12-1/8" and 12-1/4", which is way beyond the acceptable measurement. Bike Radar (below) says that any chain with a measurement of longer than 12-1/16" should be replaced, and anything beyond 12-1/8" is worn to death (their words), and a new cassette or freewheel is likely needed as well.

https://www.bikeradar.com/us/road/ge...plained-46015/