The superluminal speed of a hyperdrive was rated on a decreasing scale; the faster the hyperdrive, the lower the rating. These ratings were generally referred to as "Classes" and provided a quick, although often inconsistent or inaccurate, idea of a ship's hyperdrive speed. It was based on an asymptotic scale with Class 0.0 being infinite speed. In 30 BBY. By the end of the Clone Wars most military starships were using Class 3 or Class 2. During the Galactic Civil War, military capital ships and starfighters were generally equipped with Class 1 or Class 2, industrial freighters and haulers with Class 3 or Class 4, and civilian starships with Class 5 or above. Many vessels mounted backup hyperdrives of much higher—that is, slower—class than their primary hyperdrive.

Some starships, such as the Millennium Falcon, underwent after-market modifications to achieve ratings of Class 0.5, and Dash Rendar's Outrider also had a hyperdrive Class 0.75, which was also achieved by modifications, although tampering with the generally stable technology of a hyperdrive was considered a dangerous activity. Boba Fett's Slave I had a class 0.7 hyperdrive. Hyperdrives built by those outside the sphere of the Galactic Republic, Galactic Empire and New Republic, such as the Hapan Froond-class hyperdrive, were not classed in the standard system, as controlled comparisons were difficult to attain. Some Zonama Sekotan ships were able to achieve a Class 0.4 by combining high class hyperdrives with organic technology,[5] as did the Bes'uliik starfighter via fusion of Verpine and Mandalorian technology.

It’s interesting that people try to explain this away with all kinds of retroactive in-universe technobabble. I mean, I enjoy Star Wars just as much as the next guy but it’s abundantly clear that SW wasn’t meant to be investigated at this level. It’s space mythology, not hard science fiction. And that’s fine! We can have fun asking things like “Why is the Outer Rim considered a backwater if it only takes a few hours to get from galactic center to the rim?” and we don’t really have to stress about answers to those things as fans.