How Many Ounces in That Big Gulp? Consumers May Not Know

People aren't always savvy about accurately estimating serving sizes.

In an experiment, consumers were often off by 20 to 40 percent when estimating different-sized cups of liquid. (Photo: Paul Poplis/Getty Images)

Jun 22, 2012
Kelly Zhou has written on a variety of topics for TakePart, predominantly politics, education, and wildlife.

Consumers don’t always have a clue when it comes to accurately estimating serving sizes.

Take beverages, for example. Do you know how many ounces are in a “Double Gulp”? Pierre Chandon, a French marketing professor, wanted to know how size-savvy people really are. Chandon is currently a visiting scholar at Harvard Business School.

In an experiment, he asked 294 people to estimate how much liquid was in different cups of soda, ranging from a 12-ounce cup to that 50-ounce Double Gulp, according to an article in The New York Times.  

The participants repeatedly guessed the wrong amount, thinking that the larger cups held far less liquid than they actually did. For example, someone might assume a 50-ounce cup of soda was only 35 ounces.

The problem, the Times said, is that humans have difficulty telling when something has doubled or tripled in size.

“We tend to underestimate the increase in the size of any object,”  Chandon, director of the Paris-based INSEAD Social Science Research Centre, told the Times. “When you double the size of something, it really looks just 50 to 70 percent bigger, not twice as big.”

With much attention focused on sugar-sweetened beverages these days, the experiment presents some interesting health implications. Size may indeed matter, as consistently underestimating your food and drink intake could lead to unknowlingly taking in extra sugar and calories.

Will this information change your eating and drinking habits? If so, how? Let us know in the comments.

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