I don't own one so I cannot give you concrete advice however I did consider buying one so I did read up on them extensively. I think all Sterlingwear peacoats run at least one size small. It seems that they put some effort into their size chart but measuring sleeves from the underarm seam is strange. I think they should list the sleeve lengths from the neck, like a suit shirt. Anyways, if I were you I'd try a 40L.