17mm on a ruler is a little over 2/3 of an inch.

Here's why:

* There are roughly 25.4mm in one inch.

* 17mm is less than half of 25.4mm.

* 17mm is about 0.67 inches (17 / 25.4 = 0.669).

So, if you have a ruler with inches and millimeters, 17mm would be a little past the 2/3 mark on the inch scale.