Modal Verbs: Deber vs Tener que vs Hay que
Spanish has three ways to express obligation, all + infinitive: deber (should), tener que (have to) and impersonal hay que (one must).
Taught in: A1.2 Week 10: Travel Basics
The rule at a glance
deber / tener que / hay que + infinitive
deber = should · tener que = have to · hay que = one must
Advice, moral duty
deber
should, ought to
Debes descansar más.
You should rest more.
Strong necessity
tener que
have to, must
Tengo que ir al médico mañana.
I have to go to the doctor tomorrow.
General rule (impersonal)
hay que
one must, you need to
Hay que hervir el agua primero.
You need to boil the water first.
- Personal or not? Deber and tener que are conjugated (debo, tengo que); hay que is impersonal and always hay que.
- Deber de + infinitive is probability, not obligation: Debe de ser tarde (It must be late).
Forms
Deber + infinitive is a regular -er verb, conjugated like any regular present-tense verb. Tener que + infinitive uses the irregular forms of tener. Hay que + infinitive comes from haber and never changes for person; all three are followed by the infinitive, like other verb + infinitive patterns.
| deber | tener que | hay que | |
|---|---|---|---|
| yo | debo | tengo que | hay que |
| tú | debes | tienes que | hay que |
| él/ella/usted | debe | tiene que | hay que |
| nosotros | debemos | tenemos que | hay que |
| vosotros | debéis | tenéis que | hay que |
| ellos/ustedes | deben | tienen que | hay que |
Key differences
| Aspect | Deber | Tener que | Hay que |
|---|---|---|---|
| Strength | Weak to medium | Strong | Medium |
| Personal/impersonal | Personal | Personal | Impersonal |
| Source of obligation | Moral, internal | External circumstances | Rules, norms |
| Conjugated? | Yes (debo, debes...) | Yes (tengo, tienes...) | No (always 3rd person: hay, había, habrá...) |
| Formality | More formal | Neutral/casual | Neutral |
| Common in | Advice, formal writing | Everyday speech | Signs, instructions |
The same situation, three ways:
Debo estudiar para el examen – I should study (moral, less urgent)
Tengo que estudiar para el examen – I have to study (necessity, concrete)
Hay que estudiar para los exámenes – One must study (general truth)
When to use it
1. Deber: advice and moral duty
Moral duties, advice, expected behaviour. The conditional deberías makes it a polite suggestion.
Debes descansar más – You should rest more
Deberías llamar a tu madre – You should call your mother
Deberías comer más verduras – You should eat more vegetables (advice)
Deberías hablar con tu jefe – You should talk to your boss (suggestion)
2. Tener que: strong necessity
External obligations, necessary actions, rules and requirements, urgent needs. The obligation feels concrete and unavoidable.
Tengo que ir al médico mañana – I have to go to the doctor tomorrow
Tienes que ponerte el cinturón – You must put your seatbelt on
Tiene que terminar el informe hoy – She has to finish the report today (deadline)
3. Hay que: general rules and instructions
General rules, instructions (recipes, signs), social norms, impersonal advice. No one in particular is told.
Hay que hervir el agua primero – You need to boil the water first
Hay que ser educado – One should be polite
Hay que respetar las normas de la empresa – One must respect company rules
Hay que lavarse las manos frecuentemente – You must wash your hands often
Common mistakes
Leaving out que
Not this (incorrect): Tengo estudiar
But this (correct): Tengo que estudiar – I have to study. "Have to" is tener que: the que is always there before the infinitive.
Deber de for obligation
Not this (incorrect): Debo de estudiar
But this (correct): Debo estudiar – I should study. Deber de is for probability, not obligation.
A conjugated verb after hay que
Not this (incorrect): Hay que estudias más
But this (correct): Hay que estudiar más – You have to study more. After hay que, always use the infinitive.
Quick check
6 questions1. Which means 'You should call your mother' (advice)?
Advice uses deber; the conditional deberías makes it polite. Deber de expresses probability.
2. Complete: _____ ir al médico mañana, tengo cita. (I have to go to the doctor tomorrow)
A concrete, personal necessity: tener que + infinitive.
3. Which is the impersonal one, used on signs and in recipes?
Hay que is impersonal: it applies to everyone, not one person.
4. Which is correct?
Hay que never changes and is always followed by the infinitive.
5. What does 'Debe de ser tarde' mean?
Deber de + infinitive expresses probability.
6. How do you say 'We'll have to see'?
Hay que changes tense, not person: había que (past), habrá que (future).
Deber, tener que or hay que?
Going further
Deber de for probability, hay que in other tenses, a decision guide and more examples
Deber + infinitive vs deber de + infinitive
Deber + infinitive = obligation. Deber de + infinitive = probability: Debe de ser tarde (It must be late). In everyday speech many native speakers mix them up, but keep them apart in writing.
Hay que in other tenses
Hay que changes tense but never person: había que (imperfect), habrá que (future), ha habido que (present perfect). Tener que and deber work in every tense too: tuve que uses the preterite.
Había que esperar – One had to wait
Habrá que ver – We'll have to see
Ha habido que cancelar – It's been necessary to cancel
Quick decision guide
- Is it directed at a specific person? No → hay que. Yes → continue.
- How strong is the obligation? Advice or moral duty → deber. Strong necessity → tener que.
- Context? Formal advice → deber. Everyday obligations → tener que. Instructions and signs → hay que.
More examples
Debes llegar a tiempo – You should arrive on time (polite)
Tienes que llegar a tiempo – You have to arrive on time (required)
Hay que llegar a tiempo – One must arrive on time (norm)
Tengo que ir al médico – I have to go to the doctor (appointment)