The standard size of a credit card, according to the international standard ISO/IEC 7810 ID-1 format, is:

• Width: 3.37 inches (85.6 mm)
• Height: 2.125 inches (53.98 mm)
• Thickness: approximately 0.03 inches (0.76 mm)
• Rounded corners with a radius of about 0.125 inches (3.18 mm)

This size is consistent worldwide for credit cards, debit cards, ATM cards, and government-issued ID cards to ensure compatibility with card readers and wallets.