You can run the Octane benchmark here. It will run 13 tests in total with each one giving you a base score. The final score will be the geometric mean of all the previous scores.
I ran a few tests myself and found some interesting results. Chrome returned a score of 14,705 whereas the latest version of Firefox returned a score of 8,582. Google says that Octane can run on mobile browsers, but it crashed my phone when I tried running it on the latest version of Firefox mobile. To be fair, it's probably crashed because my phone is old and terrible. If you have a newer phone, it will probably work just fine. Just don't expect any kind of amazing results.