Now you may wonder what size you need for the perfect mug or teacup for your teas or coffee, and there are many to choose from. Traditionally though, it depends on what it is you are planning on serving in it.  From extra small to extra large and all the sizes in between, it's what's on the inside that counts.
Extra-small: less than 5 oz. Traditionally an espresso cup.
Small: 5-8 oz. Teacup.
Standard size: 9-12 oz. Regular coffee mug.
Large: 13-19 oz. Latte mug.
Extra-large: 20+ oz. Oversized or soup mug.