With cookout season approaching, we’re all stocking up on disposable plates, utensils, and cups for backyard barbecues and summer parties. On more than one occasion, I’ve found myself holding a plastic cup, looking at its lines and wondering what they’re for. So, I decided to get to the bottom of this great party mystery.
As Solo, the company behind the iconic red plastic cups, notes on its website, the three lines on its original 18-ounce Solo Cup roughly represented 1, 5, and 12 ounces. Internet lore has long suggested that those lines were intended for alcohol pours: 1 ounce for liquor, 5 ounces for wine, and 12 ounces for beer.
But that theory doesn’t fully line up with CDC guidance, which defines a standard drink as 1.5 ounces of distilled spirits, 5 ounces of wine, or 12 ounces of beer. And Solo has never said the lines were designed specifically for alcohol, either.
What’s the real purpose of the lines on plastic cups?
According to Solo, the lines serve purposes beyond measuring, but they “mean something different for everyone.”
“For some, it means a responsible pour at their next tailgate,” the brand writes. “For others, it means a more secure grip as they man the grill at the BBQ.” Solo also notes that the lines can help people stack and unstack the cups without them sticking together.
Do all plastic cups have lines?
Despite their usefulness, not all plastic cups have ridges. In fact, Solo’s newer party cup design no longer includes the classic horizontal lines. In 2025, the brand updated its cups to feature a square base and grip dots instead.
However, if you’re on the hunt for those lines, you’ll almost definitely be able to find a brand that uses them at your local grocery store—and once you do, you’ll have the perfect party conversation starter!
How do you use these lines?
