A shot isn't a standard unit of measure like a cup or a tablespoon. But in the United States, a beverage shot typically contains 1 1/2 ounces, the equivalent to 3 liquid tablespoons. Shot glasses obviously work for drink recipes, but you can also use them to measure liquid ingredients when you cook. A 1 1/2-ounce shot glass equals about 44 milliliters or 9 teaspoons.
Fill a typical 1 1/2-ounce shot glass to the very top; otherwise, you'll short the recipe a little. Because you have to fill it to the brim, you should hold the shot glass above your shaker, pot or bowl, fill it, then dump it in. This way you don't have to worry about spilling any liquid when you lift it up. You do need to be careful not to over pour, though.
Smaller shot glasses, often called "pony" glasses, hold 1 ounce of liquid. Many shot glasses also come in 2-ounce sizes. Sometimes the bigger ones have a line near the rim, which is the 1 1/2-ounce mark.