"I'll just have one glass of wine," said literally everyone ever. But if that sentiment is your holiday party mantra, you might want to consider how your supposed single serving actually measures up.
That's because, according to researchers at the University of Cambridge, wine glasses of modern-day Brits at least, are now seven times the size of their imbibing predecessors of 300 years earlier. And those glass sizes have increased most in the last two decades to accompany the rise in vino consumption.
Until the second half of the 20th century, beer and spirits dominated the British booze scene, but drinking wine nearly quadrupled between 1980 and 2004, likely due to its affordability, availability, accessibility and all those successful marketing tactics.
"Wine will no doubt be a feature of some merry Christmas nights, but when it comes to how much we drink, wine glass size probably does matter," Professor Theresa Marteau, director of the behaviour and health research unit at the University of Cambridge, said in a press release.
For the study, Marteau and her colleagues examined wine glass capacity over time to illuminate whether changes in size may have contributed to that steep rise in wine drinking over the past few decades. By scouring online info and talking with antiques glassware experts and museum curators, the researchers were able to obtain the measurements of 411 glasses from 1700 to the modern day.
What they found might be a bit disheartening to anyone who leans heavily on that "just one glass" line: Wine glass capacity skyrocketed from a mere 66 milliliters (2 ounces) in the 1700s to 417 milliliters (14 ounces) in the 2000s, with the average size of a wine glass in 2016-2017 falling around 449 millileters (15 ounces). Just for reference, in the U.S., a standard single serving of wine is 5 ounces, or roughly 148 milliliters, though pubs in the U.K. reportedly favor heftier pours.
"For the most part, this [increase] was gradual, but since the 1990s, the size has increased rapidly," study author Zorana Zupan said in the press release. "Whether this led to the rise in wine consumption in England, we can't say for certain, but a wine glass 300 years ago would only have held about a half of today's small measure."
There are lots of reasons those glasses may have gotten roomier: more affordable glass prices, innovations in technology, a healthier economy and an increased societal appreciation for wine. But it could be the people behind the bar who've demanded bigger glassware to accommodate the increasingly normalized mega-pour. Despite a 2010 regulatory requirement in England to make customers aware that more modest 125 milliliters glasses are available, most establishments opt to serve 250 milliliters at a time (or about one-third of a wine bottle).
And if your response to all of this is that you have no problem moderating your intake in the face of such generous glassware, know that researchers have also found that the strength of wine has increased over the years — in the U.K. at least. But regardless of where you reside, perhaps you'll want to pay a little more attention to how much wine you're actually downing during Christmas dinner, because apparently "just one glass" could potentially still be enough to start a major scene.