Learn Turkish: Yeni telefon eski model kadar ince. - The new phone is as thin as the old model.

In English, we put 'as' on both sides of the adjective ('as thin as'). Turkish handles this differently by putting kadar (as much as) right after the noun you are comparing it to, followed by the adjective. So, eski model kadar ince works out to 'old model as-much-as thin'.

Doesn't kadar usually need a direction ending (like -e/-a), as in eve kadar (until the house)? Why isn't it eski modele kadar?

Excellent catch! When kadar means 'until' or 'as far as' a time or place, it requires the dative (-e/-a) ending on the noun before it. However, when using kadar for comparisons of equality, regular nouns stay in their plain, dictionary form. Since we are comparing the phone to a model, it remains just eski model kadar.

Where is the word for 'is' in this sentence?

For the 'he/she/it is' form (third-person singular), Turkish often drops the 'to be' ending entirely in everyday language. You could write incedir to sound more factual or formal, but leaving it as just the adjective ince is completely natural and correct.

What is the exact word order formula for this type of comparison?