You are here

The Half-Glass Rule

Use a Simple Rule of Thumb to Avoid Drinking Too Much

Use a Simple Rule of Thumb to Avoid Drinking Too Much

To avoid over-pouring wine, only pour half a glass regardless of the glass you are pouring in

Using the half glass rule reduces the amount the average drinker pours by 18%

This rule of thumb is more important for men, who are more likely to over-pour

Scroll down to read more... 

Smarandescu, Laura, Doug Walker, & Brian Wansink (2014). Big drinkers: How BMI, gender and rules of thumb influence the free pouring of wine. International Journal of Drug Policy, 25: 1060-1065. doi:10.1016/j.drugpo.2014.07.020.

What’s the right amount of wine to pour?  Pouring the right amount of wine at home or at a dinner party can be difficult to gauge because of factors such as glass size and shape. Recent Iowa State and Cornell research has shown that people tend to pour 12% more wine when they pour into a wide wine glass rather than a standard sized one, 12% more wine when they are holding the glass (versus pouring into a glass on a table), and 9% more when they are pouring white wine into a clear glass. A new finding from the research team shows that having one simple rule of thumb can curb overpouring despite the conditions. 

“People who make it a basic policy of only pouring half a glass poured an average of 18% less regardless of what, how, or where they were pouring,” says coauthor Brian Wansink, PhD, Professor of Marketing at Cornell University and author of Slim by Design:  Mindless Eating Solutions for Everyday Life.

The study showed that those most at risk for overpouring wine are heavy males, those having a high Body Mass Index (BMI).  “If you’re a man, how much wine you pour goes up with BMI,” says lead author Laura Smarandescu, PhD, Assistant Professor of Marketing at Iowa State University,“and suggests that using rules of thumb in pouring is even more important for men than for women.”

In this new study published in the International Journal of Drug Policy,  researchers asked 74 wine drinking college students to pour a glass of wine in 16 different conditions. After accounting for varying glass sizes, pour positions, and place settings, males poured more wine than females. Men of average BMI tend to pour about 9% more wine than women of average BMI. Additionally, the higher a man’s BMI the more he is likely to pour.  However, women tend to pour about the same amount despite their BMI. Wansink, notes, “It may be that women are more in tune with social norms when it comes to drinking because intoxication is seen as less socially acceptable for women.”

According to coauthor, Doug Walker, PhD, Assistant Professor of Marketing at Iowa State, “knowing who is most likely to over-pour wine is important because it can help to increase awareness among those most at risk and it can also help us develop effective rules-of-thumb to avoid accidently over-pouring in the future such as the “half-glass” rule-of-thumb.”

Male and female participants who adopted the “half glass” rule-of-thumb, filling only half of a glass with wine, reduced pour size by about 18% regardless of BMI. “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,” Wansink advises, “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 accidently drink too much.”

Summary by Brian Wansink, PhD