All credit cards have exactly same size around the world. They are made in size of 8.56cm in width and 5.397cm in height.
Why the credit card is made in same size and how its size is decided?
The reason is to need the same standard. If the size of the card is not same each other, machines of many types such as ATM, terminals, etc. will be necessary for cards. So, all credit cards have been made by ISO international standard. ISO 7810 ID-1: 85.6 X 5.398cm (3.37 X 2.125 inches)
So, why size of credit card is decided by ISO standard?
The reason seems to apply “Golden Ratio”. Pythagoras, an ancient mathematician, suggested the golden ratio that is human recognizes the most ideally and in balance. This ratio is 1:1.6, and the popular examples are Temple of Parthenon in Greece, Pyramid in Egypt, Venus of Milos, and Mona Lisa. Additionally a book, computer monitor, A4 paper, movie screen, etc. are applied to golden ratio.
ISO standard of credit card also applies to this ratio.
Ratio of credit card 1:1.586 ≒ 1:1.6 Golden ratio
The reason why the size is applied to this beautiful ratio seems that maybe because it makes eyesight feel at ease.