Shot glasses vary in size and shape, typically holding between one to three ounces of liquid. However, many do not have indicator markings, which can make it difficult to tell the exact size of the glass. Additionally, though a standard shot of alcohol is considered to be 1.5 ounces, some establishments use one ounce of liquor per drink, depending on the proof of liquor.
Determining the volume of a shot glass by appearance alone can be difficult. The only way to be certain of the volume is by measuring the contents in a marked container like a measuring cup. Another consideration is the type of alcohol being measured, since the percentage of alcohol can vary dramatically between beverages, ranging from 5 percent to 60 percent.