The Magic Number? Here’s Why So Many Spirits Are Bottled at 80 Proof

Jack Daniel’s whiskey on a store shelf. Jack Daniel’s best-selling Old No. 7 Tennessee Whiskey is one of many 80-proof bottles you can find on shelves around the world. (Photo by Igor Golovniov / SOPA Images/Sipa USA)(Sipa via AP Images)

If you’re a regular liquor drinker, chances are you’re very used to seeing “80 proof” or “40% ABV” written on bottles. Eighty proof seems to be the magic number in some ways, but why is that? Where did that number come from, and why is most liquor bottled at 40%? Let’s break it down.

Proof and ABV — What They Mean

ABV stands for “alcohol by volume.” ABV and proof are both measurements of the alcohol content. When you see “40% ABV” or “80 proof” (proof is just ABV multiplied by two), that means the spirit in question is 40% ethanol, or alcohol.

The term “proof” originated in 16th century, when English sailors tested the strength of rum by mixing it with gunpowder. If the mixture could still ignite, this was termed “proof” that the alcohol content was high enough to support combustion. This mark became known as “100 proof,” which equated to a little over 57% ABV.

Over time, the definition of proof evolved, and in the U.S. and elsewhere, it’s defined as two times the ABV. So, a spirit that’s 40% ABV is 80 proof — pretty easy math to do, although you’ll still catch us taking a second to mentally calculate the proof of a spirit whose ABV is something like 59.65%.

Why Are So Many Spirits Bottled at 80 Proof?

This is actually a very simple answer: Economics. 80 proof/40% ABV is the legal minimum for many spirits to be bottled at in many countries, including the U.S. Eighty proof is the legal minimum in the U.S. for whiskey, tequila, gin, rum and vodka.

In most cases, the lower a spirit’s ABV, the less pure spirit is in the bottle. In other words, it’s been cut down to proof with water. The more water producers can mix in, the more money they can make, since water is a lot less expensive than liquor.

When it comes to whiskey, for example, distillers are able to maximize the number of bottles they can fill per barrel by adding the most water possible and bottling at 80 proof. This is key for larger brands that mass produce to make a profit without selling their products at high prices.

Barrel-aged liquor without any water added tends to be pricier and is referred to as “barrel proof” or “cask strength.”

Bourbon and other American whiskeys may legally be distilled to a maximum of 160 proof, or 80% ABV, but typically lose alcohol content as they age, depending on climate.

Whiskeys bottled at higher than 140 proof, or 70% ABV, are often referred to as “Hazmat proof.”

Why Is 80 the Magic Number?

It’s difficult to say with certainty how we ended up with the 80 proof minimum we have. Some say the U.S.’s standard of 80 proof originated from the English, who measured alcohol by volume (proof) and weight. The lowest proof they tolerated was about 30 degrees under proof by weight, which equates to 39.9% ABV, according to VinePair.

According to scotchwhisky.com, Scotland got its 80-proof minimum thanks to a wartime effort by the government to increase whisky taxes and then lower alcohol percentages, as David Lloyd, the secretary of state for war and later prime minister, was concerned about alcohol’s effects on the nation’s war efforts.

Not long after the wartime restrictions ended, according to scotchwhisky.com, taxes were raised, and it became financially impractical for distilleries to make stronger whisky. Eighty proof was and still is the standard.

Whatever the reason, 80 proof is the standard we have today. While most spirits enthusiasts prefer their bottles a bit higher than the minimum, 80 proof strikes a good balance for a minimum requirement; it isn’t wildly watered down and still allows the flavors of the spirit to shine through, while being economically viable for producers who want to sell affordable bottles. The lower proof also allows drinkers to enjoy more than one or two small pours without feeling awful the next day.

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