That does look a bit tight. I size up when I bought my Sandringham trench coat since the sales warn me the sleeves will be tight since it's a slim fit. I normally wear US 2, but bought a US 4 to allow more room. The trench coat still look fitted when button up. If you just brought your trench coat, I recommend you go back to try one size up, if it's too loose, you can consider Sandringham style.