As legend has it, it was while stepping into a bathtub that the mathematician Archimedes discovered his law of buoyancy. Just as submerging himself into the bathtub raised the level of water around him, he determined that could other objects could be submerged in water to calculate their volume. So elated was Archimedes by his discovery, that he jumped out of the tub and ran naked through the streets, screaming “Eureka!” A simple matter of personal hygiene had given birth to one of the most important discoveries in the history of science.

More than two millennia later, the makers of the 1988 film Willow stumbled onto a landmark achievement of their own. In setting out to make a simple fantasy adventure film, Ron Howard and company managed to do what awards shows like the Oscars have attempted for decades: create a measure by which the quality of all films may be judged. As such a stunningly average piece of cinema, Willow occupies the perfect space separating good from bad; it is the pinnacle of cinematic mediocrity. Remarkable solely for being so very unremarkable, it is the quintessential one-thumb-up, a perfect two and a half out of five stars. It’s the kind of movie you might watch on a lazy Saturday afternoon if it were on television, but only until the next commercial break. Willow is the magnetic north on the moviegoer’s compass, an essential tool in navigating and endless sea of celluloid.

In the likely event that you’ve forgotten Willow’s relatively forgettable plot, Warwick Davis plays Willow, a little person who stumbles upon the responsibility of protecting an enchanted baby from the clutches of the evil Queen Bavmorda. Joined along the way by Madmartigan (Val Kilmer, in all of his Top Gun-era glory) and a trio of cutesy-but-kind-of-annoying tiny people called brownies, Willow uses a magic twig to defeat the witch, and saves the world for annoying brownies, stilted swordsman, and adorable babies alike. It is as exciting as it is slow, as funny as it is dull, and as dazzling as it is campy—middle-of-the-road in every sense.

Willow’s lack of luster is no small achievement, however, and creating any means of measurement has far-reaching implications: before Archimedes, any old shiny yellow piece of junk could be passed off as gold; before The Willow Scale, so could any piece of trash cinema.

Consider this: you and a friend are at your favorite little coffee shop, when she mentions that she recently saw a new movie you keep hearing about. You ask her what she thought, but she’s reluctant to give a decisive answer. “Eh,” she says, contemplatively bobbing her head back and forth, “it was okay.” You press her a bit, but still she’s reticent. “It was so-so. Definitely not great,” she says.

Her response is no doubt unsatisfying. But thanks to The Willow Scale, there is a simple solution. “Was it better than Willow?” you ask her, knowing the film’s position perfectly separating good films from bad. Yes? It couldn’t be that bad. No? Not even as good as Willow? Huh. Probably not worth your time. It’s just that easy.

There are, of course, those who would attempt to challenge The Willow Scale. But these skeptics—people who probably also hate the metric system, eschew Esperanto, and oppose the flat tax—are easily accounted for: childhood nostalgia, the fear of hunky swordsmen, or a burning passion for Warwick Davis are just a few factors that might cloud one’s objectivity. Just as Copernicus was chastised for correctly asserting that the Earth orbits the son by those clinging to erroneous beliefs to the contrary, science would eventually prevail. Hard facts will expose the truth.

First, there are the critics’ reactions. Willow confounds Roger Ebert, who muses, “Willow is certainly not a breakthrough film to a mass audience, but is it at least a successful children’s picture? I dunno.” Me neither, Roger. Janet Maslin’s New York Times review is just as lukewarm, calling the film “as vast as it is secondhanded,” going on to remark that, “Willow, a pleasant but bland character, doesn’t inspire much sentiment.” Amen. And high-falutin’ critics aren’t the only ones to meet Willow with such impassioned ambivalence—viewer comments from the Internet Movie Database are equally equivocating. “This movie has everything! Well, lots of things,” raves one reviewer. Another offers this underwhelming assessment: “For its day, Willow was one of the better fantasy movies.” What does that make it today, then? Far from perfect… unless you mean perfectly average.

It’s a shame that the makers of Willow couldn’t celebrate their revelation the way Archimedes did. Their contribution to cinematic metrology is no doubt a bittersweet achievement. No one sets out to epitomize mediocrity, after all. But the rest of the moviegoing public owes them gratitude for their contribution. Before Willow, we had only unreliable, unscientific sources like the Golden Globes or the AFI’s top 100 list to measure quality. But in the past 2500 years, we’ve come a long way. Today, thanks to Archimedes, we can determine that Oscar statuettes are not composed of solid gold; and thanks to Willow, we know which movies are and aren’t worthy of winning one.