Numbers can be a drag. Especially when you're following a cocktail recipe and you encounter “1/2 glass of brandy”. Uh, what size glass? A pint glass? A wine glass? A shot glass? A search for the proper conversion can lead to interpretations that are even less helpful “1 glass = 1 wineglass.” A white wine glass? A red wine glass? Filled to the top, or three fingers from? It's enough to make you throw in the dram (whatever that is) and hit your closest local.
The following is a guide of measurements (for drinking) to help. All of them are in fluid ounces. Keep in mind that a fluid ounce and an ounce of weight are two different entities (except in the case of water and milk). Dry measurements are typically about 1/6 larger than wet.
Here is a list of conversions, with Imperial measurements (from the U.K), as well as few British ones–as both are found in many classic cocktail books and can be mighty confusing.
1 quart (Imperial) = 40 ounces
1 quart = 32 ounces
1 bottle = 24 ounces
1 pint (Imperial) = 20 ounces
1 pint = 16 ounces
1/2 pint (Imperial) = 10 ounces
1/2 pint = 8 ounces
1 gill (Imperial) = 4.8 ounces
1 gill = 4 ounces
1 dram = 1/4 tablespoon (found in the British metric system or English recipes before approx. 1972)
1 wineglass = 2 ounces
1 jigger = 1 1/2 ounces – 1 1/4 ounces
1 pony = 1 (fluid) ounce = 2 tablespoons
1 tablespoon = 1/2 (fluid) ounces
1 teaspoon = 1/16 fluid ounces
A dash is a tricky one. When applied to bitters, a “dash” makes sense: it's what comes out the top of the bottle. But if you find a recipe calling for “dashes of syrup,” check out similar drink recipes and use your judgment in how much you need.
And remember, as with most everything in this world, drinks are a matter of taste. So if you like things a little sweeter, add a “dash” more sugar or syrup. If you can't get enough mint, for the love of God throw in another spring, and if you're diabetic like Hemingway, skip the sugar and pucker up.