A drink ordered as a “Double” means that it has double the amount of alcohol in the drink, but the same amount of other ingredients. Generally a single drink contains about 1.5 ounces of alcohol, so a double will equal 3 ounces. These tend to be very strong drinks and heavily taste of alcohol.

A double shot usually contains 3 to 4 ounces of liquor. Since there is no standard size for a shot glass, there is also no standard measurement for a double shot. More American bars would consider a shot to be 1.5 oz., making a double shot 3 oz.

A 2001 amendment allowed a double shot of 70 ml to be served. Generally, a single shot is equal to 35 ml in Northern Ireland and Scotland and 25 ml in Wales and England. There is no official size for a single shot, except in Utah, where a shot is defined as 1.5 US fl oz (44.4 ml).

A standard whiskey pour is 1.5 ounces for a shot, 2 ounces for a neat or rocks pour, and 3 ounces for a double. In this case, you're drinking it straight or neat.