It's down so I can't see, but I assume this is doing a calculation I tried to do using passportindex and had trouble with:

Most passport rankings are by total number of places you can go. But given I already have one passport, what value do I get from a second passport? For example, Canada, USA, Uk, etc have fairly similar sets of countries you can go to. But maybe there's a passport that gets me access to the various middle Eastern and African countries I don't have access to. So maybe something lower overall rated is better as my 2nd passport.

Check the tab "Improve" on the passportindex.

It'll show you what you get out of a second, third etc passport.

Iran? Pakistan?

It's back up, but thanks for sharing the link for the passport index. I never knew about that site.

Down again