If you’ve ever been to a barbecue, to a college, to a party, to basically any social gathering in America, then you know the solo cup. Usually in red, these plastic cups just say, “Let’s have some fun!”— but that’s not all they’re saying. Those ridges on the side tell a story, and The Kitchn is here to pass it on to us.

So about those ridges— they’re not just for grip. It turns out, they actually mark perfect measurements for common drinks! Start at the bottom and count up:

1. First ridge = 1 ounce, for shots of bourbon, gin, and other liquors, straight up or for a mixed drink
2. Second ridge = 5 ounces, the recommended standard wine pour
3. Third ridge = 12 ounces, typical amount in a can of beer or soda
4. Fourth ridge = 16 ounces, a pint
5. Last ridge = 18 ounces, for ice overflow

It’s crazy how perfectly they match up! Officially, the company that makes solo cups, Dart Container Company, has said that this correlation is entirely coincidental, but it works too well for us to entirely believe that’s true. Take a look at what they say the measurements mean – mouthwash and chocolate syrup are both involved – here, and check out The Kitchn’s article for some more fun facts about this popular cup.

Regardless of how you use the markings, we think it’s safe to say you’re now set up to have even more fun with them this summer. Tell us— do you use these cups, or you prefer something else? Did you know this measurement secret before now?