I should probably say “att”, nothing, or “för att”, since the reason for using “att” is either as a part of the preceding verb, or used to separate clauses, and many verbs don’t require it. “För att” however, is something different.

Here are couple of sentences using “att”:

• Jag gillar att sova (I like to sleep / I like sleeping)
• Erik sa att han skulle komma (Erik said that he was going to come)

In the first sentence, the “att” is needed for the verb “gillar”. In the second one, it separates the main clause and the subclause. All good. Here is a sentence using “för att”:

• Jag gick hem för att studera. (I went home to study)

Here we have an action (jag gick hem) and a purpose (studera). I went home with the purpose of studying. This is when you use “för att”. You’re talking about an action with a purpose. Let’s compare three new sentences:

• Jag kan lära mig svenska (I can learn Swedish)
• Jag gillar att lära mig svenska (I like to learn Swedish)
• Jag studerar för att lära mig svenska (I study to learn Swedish)

The first sentence has no purpose, it just gives the information that I can learn Swedish. The verb “kan” does not require “att”. In the second sentence, the “gillar” also has no purpose. I don’t like Swedish with a purpose, it’s just a feeling. In the third sentence however, you’re studying with the purpose of learning Swedish. That’s why we use “för att”. Let’s compare two new sentences:

• Träning är ett sätt att bli stark (working out is a way to get strong)
• Jag tränar för att bli stark (I work out to get strong)

In the first sentence, we’re talking about how to get strong. We have a purpose. But we don’t have an action. “Ett sätt” isn’t an action. We’re just giving information about how to get strong. “Jag tränar” however, is an action. So we have an action with a purpose – we use “för att”. This is often confusing for people since in English we use “to” in both of these cases. But there’s a trick. If we replace “to” with “in order to”, we can easily see when to use “för att”:

• Working out is a way in order to get strong – WRONG
• I work out in order to get strong – CORRECT

So, in short, if it’s an action with a purpose, we use “för att”. If you’re not sure, check if it sounds good to say “in order to”, instead of “to” in English.

Note! In spoken Swedish, it’s common to say “för att” instead of “därför att”. For example:

• Jag gjorde det för att jag ville = Jag gjorde det därför att jag ville (I did it because I wanted to)