To compare two things and say they are equal (or not equal), in German you can use the word "so + adj. + wie". For example:
Mein Auto ist so schnell wie deines.
My car is as fast as yours.
Meine Wohnung ist so groß wie die Wohnung von meiner Mutter.
My apartment is as big as my mother's apartment.
Mein Vater ist nicht so alt wie dein Vater.
My father is not as old as yours.
Comparative in German
To compare two things that are not equal you will use "comparative + als". You can create comparative by using the basic form of the adjective and you add "er".
Often, if there is a vowel in a single-syllable adjective that can have umlaut (a, u, o), it gets the umlat.
Mein Auto ist schneller als deins.
My car is faster than yours.
Meine Wohnung ist größer als die Wohnung von meiner Mutter.
My apartment is bigger than my mother's apartment.
Mein Vater ist älter als dein Vater.
My father is older than your father.
Superlative in German
If you want to say that something is of the highest quality, you will use the construct "am + superlative". Superlative is formed by adding "sten" to the adjective.
If the adjective has "t", "d", "s", "z", "ß", "sch" or "x", it gets an "e" inserted for easier pronounciation.
Again, if there is a vowel in a single-syllable adjective that can have umlaut (a, u, o), it gets the umlat.
Mein Auto ist am schnellsten.
My car is the fastest.
Meine Wohnung ist am größten.
My apartment is the biggest.
Mein Vater ist am ältesten.
My father is the oldest.
Declension of comparative and superlative in German
If comparative or superlative versions of an adjective are used as attributes, they are declined just like base form of the adjective.
The comparative version of the adjective has "e" added and this form of the adjective is used in declensions.
The superlative version of the adjective has "n" removed and this form of the adjective is used in declensions.
Das schnellere Auto ist teurer.
The faster car is more expensive.
Das schnellste Auto ist am teuersten.
The fastest car is the most expensive.
Irregular versions
Most common irregular comparatives and superlatives are listed in the table below: