Planetary Classification

Planetary Classifications are used by space-faring civilizations to summarize a planet's overall conditions and habitability for certain species. These classifications come in two forms: Size classifications and Environmental Classifications. 

Size Classifications:

Classifications are based on the planet's radius at the equator.
Class 1: Radius > 70,000 miles
Class 2: Radius of 52576 - 70,000 miles
Class 3: Radius of 35151 - 52575 miles
Class 4: Radius of 17726 - 35150 miles
Class 5: Radius of 301 - 17725 miles
Class 6: Radius < 300 miles

Environmental Classifications:

S class: Dry planets, with less than 5% of the surface covered in water.
A class: “Balanced” planets, in temperatures between F class and C class, with enough water so as not to be a P class but not enough to be W class.
W class: Ocean planets, where more than 90% percent of the surface is covered with water or some other solvent
G class: Gaseous planets, usually gas giants.
F planets: Molten planets, with average temperatures greater then 2400 degrees F.
C planets: Frozen planets, with average temperatures less then 32 degrees F.
B planets: Planets with adverse conditions that are otherwise habitable (adverse conditions include perpetual storms, frequent volcanic activity, or occasional glass raining from the sky).