Learning Spanish would be a lot easier if it were simply a matter of translating word for word. But as you've doubtless seen already there are many instances where it's much more complicated than that. Often one word in English could be translated two different ways in Spanish (ser and estar for example) and vice versa. Spanish prepositions are a trouble spot as many of them have two or more meanings in English. Perhaps the most notorious Spanish prepositions are por and para. They can both mean "for" and it's not easy to know which one to use. Additionally, as you will see, they can both have other translations. Por and para can be difficult, but it's also important to learn the proper usage of each word.
Para is used less often and has fewer rules to learn, so we'll start there.
When to Use Para
Generally speaking para is the more specific of the two prepositions and often expresses destinations, deadlines, purposes, and opinions.
Para is used to identify a specific destination:
Salgo para escuela ahora.
I'm leaving for school now.
Se van para Madrid.
They're leaving for Madrid.
Gift / Benefit
Para is used to identify the recipient of a gift or express that something is for someone else's benefit:
El coche es para
The car is for Raúl. (The car is a gift.)
Trabajaba para Juan.
I worked for Juan. (Juan was my boss.)
El concierto fue para los granjeros.
The concert was for the farmers. (It was a benefit concert.)
Para is used to express opinion or judgment:
Para mí el fútbol es el mejor deporte.
For me soccer is the best sport.
La clase de francés es fácil para ella.
French class is easy for her.
Use / Purpose / Plan
Para is used to express a use, a purpose, or a plan. When coupled with an infinitive para means "in order to":
Es una caja para joyas.
It's a box for jewelry.
Está estudiando para ser abogado.
He is studying in order to be a lawyer.
Para is used to express a deadline or time frame:
La tarea para jueves es leer capítulo tres.
The homework for Thursday is to read chapter three.
Other Uses of Para
Para is used in incongruous descriptions (when something is diferent from what is expected):
Está bajo para su edad.
He is short for his age.
Para niña, habla bien.
For a child, she speaks well.
Note: Don't confuse the para conjugation of the verb parar ("to stop") with the preposition.
When used with estar, para means "to be about to" or "to be ready to":
Estoy para salir.
I'm about to leave.
Ahora está para escuchar.
He's ready to listen now.
There is also a handful of para expressions:
by that time
for a change
That takes care of para, what about por?
When to Use Por
Note: Over the years the phrase "por a" became the modern para.
Por occurs much more often in Spanish and has a bewildering variety of uses and translations. Por is the more general and vague of the two prepositions and it is often used with locations, times, and exchanges.
Por is used to express movement through, along, or around something:
Caminamos por la ciudad.
We walked through the town.
Paseaba por la playa.
I would stroll down the beach.
Por is used to express a substitution:
Trabajé por Juan.
I worked for Juan. (Juan was sick.)
Benito jugó por Ricardo.
Benito played for Ricardo. (Ricardo was injured.)
Por is used to express an exchange or purchase:
¿Cuánto pagaste por tu computadora?
How much did you pay for your computer?
Te doy $20 por esa gorra.
I'll give you $20 for that hat.
Note: Por is used for duration of time but para siempre means "forever."
Duration of Time
Por is used to express a duration of time:
¿Caminaste por treinta minutos?
You walked for thirty minutes?
Viajaba España por tres meses.
I traveled Spain for three months.
Por is used to express an approximate location:
Estacioné mi coche por aquí.
I parked my car around here.
Por is used to express an approximate or indefinite time:
Salgo por la mañana.
I leave in the morning.
Mirábamos la televisión por la noche.
We watched television at night.
Por is used to indicate the cause of or reason for something:
No podemos practicar por la nieve.
We can't practice because of the snow.
Manner / Means
Por is used to express manner or means of transportation or communication:
Pablo viajaba por tren.
Pablo traveled by train.
Marta me llamó por teléfono.
Marta called me on the phone.
Motive / Reason
Por is used to express a motive or reason for an action:
Fue al supermercado por cigarrillos.
He went to the supermarket for cigarettes.
Recibió un castigo por llegar tarde.
He received a punishment for arriving late.
Other Uses of Por
Por is used with to express a cause or an agent of action in passive voice sentences:
Las chozas fueron destruidas por el viento.
The huts were destroyed by the wind.
Por is used to express support or to mean "on behalf of":
Trabaja por la gente sin hogar.
She works on behalf of the homeless.
íVoto por Manuel Rosales!
I'm voting for Manuel Rosales!
When used with estar, por means "to be in favor of" or inclined to do something:
Estamos por almorzar.
We're in favor of having lunch.
When used with an infinitive por indicates an uncompleted action or that something remains to be done:
Hay mucho trabajo por hacer.
There's much work to be done.
Por is used with units of measurement:
Compramos gasolina por galón.
We buy gasoline by the gallon.
Por is used as the equivalent of the English word "per":
Ellas viajaban 100 millas por día.
They traveled 100 miles per day.
Por is used to signify multiplication:
Tres por tres son nueve.
Three times three is nine.
Por is also used in dozens of expressions such as:
por lo general
por lo menos
por lo tanto
por lo visto
por un lado
on the one hand
Buscar, Esperar, and Pedir
You may be tempted to use either por or para after the verbs buscar (to look for), esperar (to wait for), or pedir (to ask for) but you shouldn't. Remember that the "for" is built-in to each of these verbs so adding por or para would be redundant. Just add the direct object immediately after the verb instead:
Busco un apartamento.
I'm looking for an apartment.
Esperan el autobús.
They are waiting for the bus.
Me pidió un favor.
She asked me for a favor.