Mazda arrived at the CX-30 name because of a self-created problem: the Chinese Mazda CX-4. The CX-4 name would be perfect for the CX-30, since it would fall right between the CX-3 and CX-5 where it's positioned. But with the name taken, and evidently no plans to discontinue, replace, or rename that Chinese model, Mazda needed something else, and fractions and decimals weren't on the table. So appending a zero was the plan.
Talking with a Mazda representative, there were hints, though no concrete confirmation, that this naming scheme could possibly spread throughout the Mazda line. There would be advantages to such a system, such as bringing the CX-30 into line with other Mazda products, but it would also provide room for other in-between models named CX-35, CX-25, etc.
Now for the size. Mazda says it fits between the CX-3 and CX-5, both of which will be sold alongside it for the foreseeable future. But is it closer to one than the other? Length-wise, the CX-30 is 4.7 inches longer than the CX-3 and 5.9 inches shorter than the CX-5. It's also an inch wider than CX-3 and 1.8 inches narrower than CX-5. Interestingly, the CX-30 and CX-3 are the same height, which is 5.9 inches shorter than the CX-5. The CX-30 does have a bit more ground clearance than the CX-3, but only by a few hundredths of an inch.
To add some context outside the Mazda brand, the CX-30's size also puts it on par with crossovers such as the Mitsubishi Eclipse Cross, Subaru Crosstrek and Jeep Compass. All of those are sort of in-betweeners themselves. By contrast, the CX-3 is one of the smallest subcompact crossovers and aligns more closely with a Hyundai Kona.
In other words, there actually was a segment gap Mazda could fill as the CX-30 fall pretty squarely between the CX-3 and CX-5. As such, we also imagine that pricing will fall between the two. The CX-3 starts at $21,435 and the CX-5 at $25,395. So about $23,000 seems reasonable for the base Skyactiv 2.0-liter engine, and probably more for the Skyactiv-X engine.
That also brings us to some of the mechanical differentiation that puts the CX-30 in between the two other Mazda crossovers. The 2.0-liter engine will be similar in power to the engine in the CX-3, with the Skyactiv-X engine closer in power to the base 2.5-liter in the CX-5. Mazda's turbocharged engine would still be an exclusive upgrade for the CX-5 among the compact crossover trio.
Additionally, the CX-30, while not having the most powerful engines, will boast the platform and suspension from the excellent new Mazda3. By contrast, the CX-3 is based on the aging Mazda2, while the CX-5 is an evolution of the existing Mazda platform shared with vehicles such as the Mazda6 and outgoing Mazda3.