Every language needs a way to say if this happens, then that happens. In Spanish, these if-then sentences are built with si (if), and they come in three types. The good news is that each type follows a fixed formula. Once you know which tense goes on each side of the comma, conditional sentences become one of the most predictable corners of Spanish grammar.
In this article we will look at each type one by one, with a quick detour to review the imperfect subjunctive, the tense that powers Types 2 and 3.
First, a spelling note: si is not sí
Si, with no written accent, means if. Sí, with a written accent, means yes. The accent mark is the only thing that separates them in writing, so keep an eye on it.
Si quieres, vamos al cine. (If you want, we can go to the movies.)
Sí, quiero ir al cine. (Yes, I want to go to the movies.)
You can check both entries in the Real Academia Española's dictionary: si and sí.
Type 1: Real or likely conditions
We use Type 1 when the condition is real or likely, and its fulfillment guarantees an obvious result. Everything stays in the indicative. There are two versions of the formula:
Si + present, present
Si + present, future
Use the all-present version for general truths and habits:
Si no desayuno, no me concentro bien en los exámenes. (If I don't eat breakfast, I don't concentrate well during exams.)
Si llegas tarde a la estación, pierdes el tren. (If you arrive late at the station, you miss the train.)
Si llueve, no salgo a correr. (If it rains, I don't go running.)
Use present + future when the result is a specific prediction:
Si tomas el tren de las siete, llegarás a la entrevista con tiempo de sobra. (If you take the seven o'clock train, you will arrive at the interview with plenty of time to spare.)
Si estudias un poco cada día, aprenderás mucho más rápido. (If you study a little every day, you will learn much faster.)
Si Marta llega temprano, cenaremos juntos. (If Marta arrives early, we will have dinner together.)
Notice that the verb after si is in the present indicative in both versions. Only the result clause changes.
Type 2: Imaginary suppositions
Type 2 is for imaginary suppositions: situations that are not real, but that we want to imagine. Think of English sentences like If I won the lottery... The formula:
Si + imperfect subjunctive, conditional
Si yo ganara la lotería, dejaría de trabajar mañana mismo. (If I won the lottery, I would stop working tomorrow.)
Si Irene me escribiera, le contaría la verdad. (If Irene wrote to me, I would tell her the truth.)
Spanish borrows the imperfect subjunctive to build the supposition the same way English borrows the past tense: if I worked is si yo trabajara. Neither language is really talking about the past here. The two halves line up like this:
If I lived closer to the station → (then) I would take the train every day.
Si yo viviera más cerca de la estación → (entonces) yo tomaría el tren todos los días.
The order is flexible. Sometimes we say the conditional first and the supposition after:
Dejaría de trabajar mañana mismo si ganara la lotería. (I would stop working tomorrow if I won the lottery.)
Le contaría la verdad a Irene si me escribiera. (I would tell Irene the truth if she wrote to me.)
Notice when we do this we drop the comma.
The result clause uses the simple conditional (dejaría, contaría, tomaría). If you need to review how to form it, we cover it in detail in our guide to the Spanish conditional tense.
Refresher: Forming the imperfect subjunctive
Take the third-person plural of the preterite, drop the ending -ron, and add the endings -ra, -ras, -ra, -ramos (with a written accent on the vowel right before it), -rais, -ran.
Cantar (cantaron):
cantara, cantaras, cantara, cantáramos, cantarais, cantaran
Comer (comieron):
comiera, comieras, comiera, comiéramos, comierais, comieran
Vivir (vivieron):
viviera, vivieras, viviera, viviéramos, vivierais, vivieran
Irregular preterites carry their irregularity straight into this tense:
tener: tuvieron → tuvieran
estar: estuvieron → estuvieran
hacer: hicieron → hicieran
poder: pudieron → pudieran
ser and ir: fueron → fueran (context tells you which verb it is)
decir: dijeron → dijeran
There is also an alternative form ending in -se (cantase, comiese, viviese) that is still in use. For a broader review of this mood, see our comprehensive subjunctive cheat sheet.
More Type 2 examples
Si hiciera menos frío, saldría a caminar por las tardes. (If it were less cold, I would go out for a walk in the evenings.)
Saldría a caminar por las tardes si hiciera menos frío. (I would go out for a walk in the evenings if it were less cold.)
Si tuviera la respuesta, te la diría. (If I had the answer, I would tell you.)
Te la diría si tuviera la respuesta. (I'd tell you if I had the answer.)
¿Qué harías si ganaras la lotería? (What would you do if you won the lottery?)
Type 3: Rewriting the past
Type 3 looks back at a past that is already settled and imagines it going differently: the train you didn't catch, the forecast you didn't check. For this we need two compound tenses, both built with the verb haber:
Si + pluperfect subjunctive (hubiera + past participle), conditional perfect (habría + past participle)
For the supposition, conjugate haber in the imperfect subjunctive:
hubiera, hubieras, hubiera, hubiéramos, hubierais, hubieran
For the result, conjugate haber in the conditional:
habría, habrías, habría, habríamos, habríais, habrían
Here is the pattern side by side:
If I had taken the earlier train → (then) I would have arrived on time.
Si yo hubiera tomado el tren anterior → (entonces) yo habría llegado a tiempo.
More examples:
Si hubiera visto el pronóstico, no habría salido sin paraguas. (If I had seen the forecast, I would not have gone out without an umbrella.)
Si me los hubieras pedido, te habría prestado mis apuntes. (If you had asked me, I would have lent you my notes.)
Te habría prestado mis apuntes si me los hubieras pedido. (I would have lent you my notes if you had asked me.)
Si yo hubiera salido antes, no habría perdido el tren. (If I had left earlier, I would not have missed the train.)
No habría perdido el tren si hubiera salido antes. (I would not have missed the train if I had left earlier.)
Si no hubiera nevado tanto durante la noche, los trenes no habrían llegado con retraso toda la mañana. (If it had not snowed so much during the night, the trains would not have been running late all morning.)
Si me hubieras escrito antes del examen, te lo podría haber explicado. (If you had written to me before the exam, I could have explained it to you.)
A note on that last one: in English, could can carry the conditional meaning by itself, without would. Spanish does the same job with poder in the conditional (podría).
One regional note. Plenty of native speakers repeat hubiera in the result clause rather than switching to habría: Si yo hubiera tomado el tren anterior, yo hubiera llegado a tiempo. You will hear this version a lot, and it is accepted, but as a learner you are better off keeping the two halves distinct: hubiera for the supposition, habría for the result.
Mixing Types 2 and 3
The supposition and the result are independent. They don't have to be in the same time frame, which means we can combine Types 2 and 3. A condition that failed in the past can have a consequence in the present:
Si me hubiera preparado mejor para la entrevista, ahora tendría ese puesto. (If I had prepared better for the interview, I would have that job now.)
Ahora tendría ese puesto si me hubiera preparado mejor para la entrevista. (I would have that job now if I had prepared better for the interview.)
Si hubieras estudiado ayer, hoy no estarías tan nervioso por el examen. (If you had studied yesterday, you would not be so nervous about the exam today.)
Si yo hubiera mirado el horario, Marta no estaría esperándome en la estación ahora. (If I had checked the schedule, Marta would not be waiting for me at the station now.)
The pattern is simple: the hubiera clause sets up something that didn't happen in the past, and the simple conditional describes the present consequence.
One rule to remember: No present subjunctive after si
Learners often want to say si tenga because si feels like a subjunctive trigger. It isn't. After si, you will use the present indicative (Type 1), the imperfect subjunctive (Type 2), or the pluperfect subjunctive (Type 3). The present subjunctive never appears after si.
Say si tengo tiempo or si tuviera tiempo, never si tenga tiempo.
The three formulas, one more time
Type 1, real or likely conditions: Si + present, present or future. Si llueve, no salgo. Si llueve, no saldré.
Type 2, imaginary suppositions: Si + imperfect subjunctive, conditional. Si lloviera, no saldría.
Type 3, unreal past: Si + pluperfect subjunctive, conditional perfect. Si hubiera llovido, no habría salido.
Mixed 3 + 2: Si + pluperfect subjunctive, conditional. Si hubiera llovido, ahora no estaría aquí.
Memorize the pairings, practice flipping the clause order, and build your own examples. The formulas do the heavy lifting. The rest is just practicing and getting good at conjugating verbs.