Deber v Tener Que
Is there an "official" explanation as to when one uses "deber" or "tener que" ?
The English "must" and "to have to" can be explained .
Gracias.
2 Answers
From what I've heard I understand the two to be as follows....
Debo irme (I should go) = It's a good idea but I'm not obligated to do so.
Tengo que irme (I have to go) = A bit stronger than "deber" because I have a reason that I need to go.
The verb deber and the verb phrase tener que are the two most common ways of expressing obligation in Spanish, to say that someone has to, should, ought or must do something. They are followed by the infinitive form of the verb.Tener que and deber are usually interchangeable. However, tener que usually expresses a stronger sense of obligation than does deber. The phrase no tener más remedio que is one of the most common ways of expressing extremely strong obligation. A weaker sense of obligation can be expressed by using the conditional form of deber. The conditional forms of deber are especially common in questions. A vague sense of obligation can also be expressed by use of haber de, although it isn't used in all areas and can sound stuffy. Example: He de estar a dieta, I need to be on a diet. Sometimes the verb necesitar is also used as equivalent of tener que or deber, although it is less common than the corresponding English verb, "to need."
I would say "I should go" = " Debería ir(me)" not sure about the me 
- ian-hill
I don't think a native Spanish speaker thinks of it quite that way. And yes you need to use "irme" ...because irse = leave ...and ir = go (period)
Debo irme - I should be going(leaving).
Here is something: deber
