Has anyone bought any of the t-shirts that are offered in the Mastodon Shop? I want to buy one but I'm not sure what size to get. The website measures t-shirt sizes by "chest width," which must be an European thing cuz I've never seen clothes measured like that in the US.

My chest is about 20 inches wide, which would put me in a Small size according to their size chart. But I normally wear an extra large so I don't think that's right.

Can anyone explain? Help!

https://shop.joinmastodon.org/products/mastodon-my-friends-are-not-for-sale-unisex-t-shirt