Proof is the measure of alcohol in any distilled liquid. If, after a few cocktails you're still interested in doing the math, a liquor's alcohol content can be determined by halving the proof.

Most liquor is about 80 proof, or 40 percent alcohol. Wine is typically 20 to 25 proof and beer about 12 proof (now you try it). Pure alcohol, which is 200 proof, is colorless, flavorless, and, believe it or not, odorless.

What you smell and taste in an unbalanced cocktail are the impurities from the flavoring and coloring additives.

When purchasing alcohol for cocktails, 80 to 100 proof will suffice unless you're into flaming drinks. Generally, the lower the proof at distillation and the higher the proof at bottling, the better the product. A low proof early on means that more natural flavors are retained, and nasty additives avoided. The higher proof at bottling reflects less water being added.