Standard US specifications for the standard business card size is 2.0” x 3.5”.
Acceptable variations include the fold-over card: 4.0” x 3.5”, but folded to 2” x 3.5”
To a lesser degree you can also select a mini-card. These mini-cards can be as small as 1.75” x 2” and as large as 2.5” x 2.5” with several sizes in between.
We suggest that you think carefully about who will receive your business cards before you decide on non-standard sizes. While unusual shapes may be perfect for an artistic audience, business people generally keep cards in organizers or apps specifically designed for 2” x 3.5”
That doesn’t mean you must conform to the rectangular crowd. Rounded corners can make your cards stand out. Your options for rounded corners include radii of 1/8”, ¼”, 3/8” or ½”. You also have the option to cut off the top corners, bottom corners or all four corners.
Personal suggestion: Avoid round, hexagonal or octagonal business cards. Yes, they are unique. But have you ever tried getting something round out of your wallet or purse?