There are 768 US teaspoons in a US fluid gallon and 768 imperial teaspoons in an imperial gallon.
1 Gallon [Fluid] = 768 Teaspoons [Fluid US or UK]
1 Gallon [Dry] = 893.681044 Teaspoons [Dry]
Gallon is an imperial and US Customary unit. There is one type of gallon in imperial system and 2 types (liquid and dry) in US Customary system. The abbreviation is "gal".
Teaspoon is a frequently used volume unit in cooking recipes and prescriptions. 1 US teaspoon is about 5 mL and 1/6 of a fluid ounce. The abbreviations are "tsp", "ts".