Looking at the glass half full not only makes you happier, healthier, and wealthier, it also makes you a good wine drinker. Since wine is generally self-poured in various settings, such as at home, restaurants, receptions, and parties, we are left in charge of our alcohol intake, which may spark the thought: What’s the right amount of wine to pour? According to a recent study forthcoming in the International Journal of Drug Policy, adopting a simple “rule of thumb,” such as the half-glass rule, can help avoid accidentally over-pouring in the future.

“It is essential for all drinkers, especially men of higher BMIs, to have a rule of thumb for self-serving because eye-balling a serving size is a difficult task and will often lead people to pour too much,” said Brian Wansink, a professor of marketing and director of the Cornell Food and Brand Lab, on the university’s website. Free-pouring wine increases the tendency to over consume because it is not as easily measured as beer or spirits. Therefore, it is important to be aware of the environmental cues and other factors that impact pouring to help monitor drinkers' intake.

In an effort to determine what influences the free pouring of wine, a team of researchers from Iowa State and Cornell University, led by Laura Smarandescu, an assistant professor of marketing at Iowa State, looked at a variety of factors to understand and control over-pouring. A variety of pouring scenarios and rules-of-thumb were analyzed to determine how it affects the quantities of alcohol poured by men and women across body mass index (BMI) categories. The study looked only at pours, not consumption.

A total of 74 female and male college students were asked to pour wine in 16 different conditions so the researchers could control for size, shape, and color of the glass, as well as if wine is poured with a meal. The participants poured both red and white wine from bottles with different levels of fullness. They were instructed to pour as much wine as they normally would in one setting.

The findings revealed BMI affected how much men poured, but had no influence on women. However, when people used a rule of thumb, such as a half-glass or a two-fingers-from-the-top rule when pouring wine, they generally poured less regardless of BMI or geneder. “About 70 percent of the people in the sample used the half-glass rule, and they poured significantly less by about 20 percent,” said Smarandescu, in the Iowa State University press release. “It’s a big difference. We would suggest using a rule of thumb with pouring because it makes a big difference in how much people pour and prevents them from overdrinking.”

Overweight or obese men who did not use a rule of thumb, poured 31 percent more, while men at the midpoint of the normal BMI range poured 26 percent more. In women, BMI did not affect how much they poured, but those at the midpoint of the normal BMI poured 27 percent less when using the half-glass rule than those who did not. The researchers expected women to pour less than men, but expect BMI would not be an influencing factor.

Smarandescu and her colleagues believe this impact is due to social norms. They say women are more likely to socially compare with other women and are aware drinking is not as socially acceptable for women as it is for men, although it is becoming more acceptable than in the past. “[F]or men, there is still more of a culture of drinking and pouring more,” she said.

While the researchers did expect men to pour more than women, they were surprised that the half-glass rule would be an exception to men pouring more. The rule of thumb is so strong and effective that men at all levels of BMI who adopted this rule, actually poured less than women who were not using a rule of thumb. This suggest a half-glass or a two-fingers-from-the-top rule could be an effective strategy to reduce over-pouring and drinking too much.

Although this can help curb binge drinking, a 2013 study published in the journal Substance Use & Misuse found the shape and size of the glass you use can influence how much you pour. People tend to pour 12 percent more wine when they pour into a wide wine glass rather than standard sized one, 12 percent more wine when they are holding the glass (compared to pouring into a glass on a table), and nine percent more when they are pouring white wine into a clear glass. The researchers suggest sticking to the narrow wine glasses, and only pour if the glass is on the table or counter, and not in your hand. This will lead to pouring nine to 12 percent less.

These studies highlight the importance of rules of thumb when it comes to drinking, especially wine. This can help curb the high binge drinking rates in colleges, as about half of college students who drink also consume alcohol through binge drinking, according to the National Institute on Alcohol Abuse and Alcoholism. Glass half-full can be a good prevention strategy to reduce the unfortunate consequences of drinking, like death, assault, and sexual abuse.

So, “Next time you open a bottle, serve yourself a half glass — regardless of the size of your glass — and you will be less likely to accidentally drink too much,” Wansink said.


Smarandescu L, Walker D, Wansink B. Big Drinkers: How BMI, Gender and Rules of Thumb Influence the Free Pouring of Wine. International Journal of Drug Policy, forthcoming. 2014.

Smarandescu L, Walker D, Wansink B. Half full or empty: Cues that lead wine drinkers to unintentionally overpour. Substance Use & Misuse. 2013.