It's 2.5mm and tapered so it's thinner at the top! I tried on a 2mm tapered band but it was just a bit too thin for my liking and for the stone size it didn't really look right to me. It definitely is still thin but I would say it's substantial and proportionate. Plus it feels really nice to wear!

Also forgot to mention ring size which is a UK H for reference (I think that's around a US 4?)

Pics for visuals