PARA or POR? 4

Para — expressing standard or comparison — Para can mark a standard against which something is measured or a surprising contrast: Para ser principiante, habla muy bien (For a beginner, she speaks very well). Para lo que ganamos, el apartamento es caro (Given what we earn, the flat is expensive).

Por — rate and proportion — Por expresses rates and proportions: 80 km por hora, diez euros por persona, dos veces por semana, el 20% por ciento. It answers "per what unit". This use overlaps with English "per" and is consistent: the unit of measure always follows por.

Same sentence, different meaning — The preposition changes the entire meaning: Lo hice por ti (I did it because of you / for your sake) vs Lo hice para ti (I did it for you / intended for you). Salió por la puerta (left through the door) vs salió para la puerta (headed toward the door).