Which category of Play Store should my utility app be in?

Hi,
Have a good weekend to you all.

I have an accurate unit converter app which is distributed on Google Play.
I just wonder which category of Play Store the app should be in in order that this utility app could be discovered easily.
Is it Productivity or Tools?

Thank you very much in advance.

I am getting confused just because of the Play Store guide about category example.
https://support.google.com/googleplay/android-developer/answer/113475

According to this guide(Categories -> Apps -> Category examples), a "conversion" app should be in category of "Productivity".

But in fact, I found so many unit converter apps are in category of "Tools" on Play Store.

So how should I make a choice?

— modified on Aug 1, 2016, 3:26:28 AM

But now you may find there are so many similar unit converter apps in category of "Tools" on Play Store.