When to use Por and Para in Spanish

It is usually hard to decide when to use Por or Para in Spanish. This is because in English you would use just For in both cases.

After many years teaching Spanish my experience has told me that a literal translation not always works and sometimes it is better to use a concept to remember what word to use in a given context:

 

POR has a meaning of passage, exchange and duration. It is the way of an action.

Examples:

Thanks for your help = Gracias por tu ayuda

I work for 8 hours = Trabajo por 8 horas

 

PARA has a meaning of purpose. It is the other end of an action

The cake is for Maria = La tarta es para Maria

Estoy preparando mi clase para mañana = I am preparing my class for tomorrow