In the metric system, 50 mL is equal to 50 millilitres, which is about 1 2/3 fluid ounces in the U.S. customary system. In recipes, 50 millilitres equals 1/4 cup.
In the metric system, a litre is the standard way to measure volume. A millilitre is one-thousandth of a litre, and it is used to measure small amounts. For liquid ingredients in recipes, most of the world uses millilitres as the unit of measure.
A single shot of liquor is 50 millilitres in Russia, Israel, and Brazil, among other places. In the United States, a single shot is 1.5 fluid ounces, which is 44 millilitres.