Conditional Sentences with Si in Spanish

In Brief

Use si + present indicative for an open or realistic condition: Si vienes, cenaremos juntos (“If you come, we’ll have dinner together”). Use si + imperfect subjunctive + conditional for an unlikely, imaginary, or contrary-to-fact present situation: Si tuviera tiempo, viajaría (“If I had time, I would travel”). Do not normally put the present subjunctive or future tense directly after conditional si.

Overview

A conditional sentence connects a condition—the circumstance that must hold—with its result. In Si llueve, nos quedamos en casa, si llueve gives the condition and nos quedamos en casa gives the result. Either part can come first: Nos quedamos en casa si llueve. When the si clause comes first, a comma normally separates it from the result.

At B1, the central contrast is between conditions treated as real or open and conditions presented as hypothetical. Spanish marks that contrast through the verb mood. The indicative presents information as real, expected, or open; the subjunctive (a set of verb forms used when a situation is not presented as a straightforward fact) helps mark an imagined or remote condition.

English and Spanish often express the same contrast, but their forms do not match word for word. English says “If I had time,” although the meaning is about now; Spanish requires the imperfect subjunctive si tuviera tiempo, not the ordinary past si tenía tiempo. Learning the patterns as complete pairs is more reliable than translating each verb separately.

How It Works

Real and open conditions

Use the present indicative after si when the condition is possible, repeated, or generally true. The result clause can use several forms depending on the intended meaning.

Meaning	Pattern	Example	English
General fact or habit	si + present, present	Si hace frío, llevo abrigo.	If it is cold, I wear a coat.
Likely future result	si + present, future	Si hace frío, llevaré abrigo.	If it is cold, I will wear a coat.
Planned or immediate result	si + present, present	Si terminas pronto, vamos al cine.	If you finish early, we’re going to the cinema.
Instruction or invitation	si + present, imperative	Si tienes dudas, pregúntame.	If you have questions, ask me.
Possible result	si + present, poder/deber + infinitive	Si quieres, podemos esperar.	If you want, we can wait.

The important point is that a future meaning does not require a future tense after si. Spanish says Si vienes mañana..., literally using the present “if you come,” not si vendrás.

Hypothetical present or future conditions

For a situation imagined as unlikely, remote, or contrary to present fact, use this pair:

Condition	Result
si + imperfect subjunctive	simple conditional
Si tuviera más tiempo,	aprendería japonés.
If I had more time,	I would learn Japanese.

The imperfect subjunctive has two standard sets of endings, in -ra and -se: tuviera/tuviese, fuera/fuese, pudiera/pudiese. Both are correct, but the -ra forms are more frequent in everyday usage across much of the Spanish-speaking world.

A hypothetical clause does not always mean that the condition is impossible. It can make a suggestion more tentative or polite:

• Si habláramos con Ana, quizá encontraríamos una solución. — If we spoke to Ana, perhaps we would find a solution.
• Si pudieras enviármelo hoy, te lo agradecería. — If you could send it to me today, I would appreciate it.

The result is often conditional, but context may call for another form. An imperative can express advice: Si yo fuera tú, no aceptaría is the usual neutral pattern, while Si tienes ocasión, llámame remains a real condition.

The order of the clauses

The order changes emphasis, not the basic meaning:

• Si vienes, estaré contento. — The condition is presented first.
• Estaré contento si vienes. — The result receives the opening emphasis.

Use a comma after an initial si clause. A final short si clause normally has no comma.

A quick decision guide

1. Is the condition a real possibility, habit, or general truth? Use si + indicative.
2. Are you imagining a different present or a remote future? Use si + imperfect subjunctive, usually followed by the conditional.
3. Are you imagining a different past? Use the advanced past pattern explained below.

Examples in Context

Spanish	English	Note
Si vienes, estaré contento.	If you come, I’ll be happy.	Open future condition
Si llueve, nos quedamos en casa.	If it rains, we stay / we’re staying home.	Present result
Si calientas hielo, se derrite.	If you heat ice, it melts.	General truth
Si ves a Marta, dile que me llame.	If you see Marta, tell her to call me.	Imperative result
Si quieres, podemos pedir otra cosa.	If you want, we can order something else.	Offer with a modal verb
Si tuviera dinero, viajaría por Sudamérica.	If I had money, I would travel around South America.	Hypothetical present
Si fuera rico, compraría una casa junto al mar.	If I were rich, I would buy a house by the sea.	Contrary to present fact
Si vivieras más cerca, nos veríamos a menudo.	If you lived closer, we would see each other often.	Imagined alternative
Si pudieras elegir, ¿qué harías?	If you could choose, what would you do?	Hypothetical question
Llevo un paraguas por si llueve.	I’m taking an umbrella in case it rains.	Precaution; indicative after por si
He guardado una copia por si acaso.	I’ve kept a copy just in case.	Por si acaso used alone
Habla como si lo supiera todo.	He talks as if he knew everything.	Como si + imperfect subjunctive
Si hubiéramos salido antes, no habríamos perdido el tren.	If we had left earlier, we would not have missed the train.	Unreal past; advanced pattern

Common Mistakes

Putting the future tense after conditional si

• Wrong: Si vendrás mañana, cenaremos juntos.
• Right: Si vienes mañana, cenaremos juntos.
• Why: In an ordinary open condition, Spanish uses the present indicative after si, even when the condition refers to the future.

Using the conditional in both clauses

• Wrong: Si tendría dinero, viajaría.
• Right: Si tuviera dinero, viajaría.
• Why: The hypothetical condition takes the imperfect subjunctive; the result takes the conditional. Although conditional forms after si occur regionally and in some special meanings, they are not the standard form for this pattern.

Using an ordinary past for a present hypothesis

• Wrong: Si tenía más tiempo, aprendería japonés.
• Right: Si tuviera más tiempo, aprendería japonés.
• Why: Tenía normally describes an actual past situation (“when/if I had time in the past”). Tuviera creates the imagined present condition.

Using the present subjunctive after si

• Wrong: Si tengas tiempo, llámame.
• Right: Si tienes tiempo, llámame.
• Why: Conditional si does not normally take the present subjunctive. This differs from expressions such as cuando tengas tiempo, where the future event is pending.

Confusing si and sí

• Wrong: Sí tienes tiempo, llámame.
• Right: Si tienes tiempo, llámame.
• Why: Unaccented si means “if.” Accented sí means “yes” or functions as a stressed pronoun: Sí, lo haré; lo hizo por sí mismo.

Treating por si as a literal si clause

• Wrong: Llevo un paraguas por si llueva.
• Right: Llevo un paraguas por si llueve.
• Why: Por si means “in case” and normally takes the indicative. It describes a precaution against something considered possible.

Usage Notes

Real does not necessarily mean certain

A “real” condition is simply left open: the speaker does not present it as imaginary. Si mañana llueve, cancelaremos el picnic does not claim that rain is likely; it only treats rain as a genuine possibility. By contrast, Si mañana lloviera, cancelaríamos el picnic makes the possibility sound more remote, tentative, or hypothetical.

Compare:

Spanish	Usual effect
Si me ayudas, terminaremos antes.	Your help is a realistic possibility.
Si me ayudaras, terminaríamos antes.	The request is more tentative, or your help seems less likely.

Tone and context matter. The second version may be diplomatic rather than pessimistic.

Present tense for habitual past is not enough

When describing repeated conditions in the past, Spanish can use the imperfect indicative in both clauses: Si hacía buen tiempo, íbamos a la playa (“If/Whenever the weather was good, we went to the beach”). Here si is close to “whenever,” and both events actually occurred. This is different from Si hiciera buen tiempo, iríamos a la playa, which imagines good weather and a possible trip.

Por si and por si acaso

Por si introduces a possible event that motivates a precaution:

• Te dejo mi número por si necesitas ayuda. — I’ll leave you my number in case you need help.
• Compra pan por si acaso vienen más personas. — Buy bread just in case more people come.

Por si acaso can also stand alone: Lleva efectivo, por si acaso (“Take cash, just in case”). Acaso adds emphasis but does not change the basic construction.

Beyond the Basics: Advanced Use

Unreal conditions in the past

To imagine a past that did not happen, use the pluperfect subjunctive (a form meaning “had done” inside a non-real clause) after si. The result usually uses the conditional perfect (“would have done”):

Condition	Result
si + hubiera/hubiese + past participle	habría + past participle
Si hubiéramos reservado,	habríamos conseguido mesa.
If we had booked,	we would have got a table.

The past participle is the verb form used with haber, such as salido, visto, or hecho. Both hubiera and hubiese are standard. In actual Spanish, the pluperfect subjunctive sometimes also appears in the result clause—Si lo hubiera sabido, no hubiera ido—especially in speech. The habría ido version is the clearest neutral model for learners.

Mixed conditionals connect different times:

• Si hubiera estudiado medicina, ahora sería médico. — If I had studied medicine, I would be a doctor now.
• Si fuera más organizado, no habría perdido el documento. — If I were more organised, I would not have lost the document.

Como si: “as if”

Como si is followed by the imperfect or pluperfect subjunctive because it presents a comparison as imagined rather than asserted as fact:

• Me trata como si fuera un niño. — She treats me as if I were a child.
• Actuó como si no hubiera pasado nada. — He acted as if nothing had happened.

Use the imperfect subjunctive for a simultaneous or general comparison and the pluperfect subjunctive for an earlier event. Do not copy the real-condition pattern here: como si es is not the standard construction.

Cases where future or conditional after si can be legitimate

The beginner rule “never use future or conditional after si” is a useful shortcut, but it is not absolute. These forms can occur when si means something other than an ordinary condition—for example, uncertainty in an indirect question: No sé si vendrá (“I don’t know whether he will come”), or echoing another person’s claim: Si será tan fácil... (“If it really is going to be so easy...” with a doubtful tone). These are separate uses of si and do not alter the core conditional patterns.

Practice Tips

1. Build two versions of the same idea. Start with Si tengo tiempo, iré and change it to Si tuviera tiempo, iría. Say what shift in attitude the new verb pair creates.
2. Memorise pairs, not isolated forms. Practise si puedo → lo haré beside si pudiera → lo haría. This makes the mood pairing automatic.
3. Notice the speaker’s viewpoint. When reading or listening, mark each si clause as open, habitual, hypothetical present, or unreal past. Then check the verb in the result clause.

Related Concepts

• Prerequisite: Simple Conditional — supplies result forms such as viajaría, haría, and podríamos.
• Useful foundation: the present indicative — used after si for open conditions, habits, and general truths.
• Next step: the imperfect subjunctive — needed for hypothetical present and future conditions.
• Advanced next step: the pluperfect subjunctive and conditional perfect — used for unreal past and mixed conditional sentences.