Kilo Lingo
Spanish grammar Part of Chapter 27

CEFR B1-B2

4 min read

Test yourself (22 questions)

Future and Conditional of Probability in Spanish

By Michael McGettrick and Sergio Linares-HernandesUpdated 12 October 2026

Spanish guesses with tenses. The future guesses about now; the conditional guesses about the past:

Quick check

Three quick questions on what you have just read. The full practice is further down.

Spot the mistake

0/3

Each sentence has one mistake. Tap it.

  • ¿ ? - I wonder what time it is.
  • . - It was probably about three.

The four guesses on one screen

future: a guess about nowconditional: a guess about the pastWhat do the colours mean?
CertainThe guessEnglish
he/she is probably
he/she was probably
ha he/she must have arrived
he/she had probably arrived

The blue box is a future form, a guess about now. The dashed pink box is a conditional form, a guess about the past. The forms are the ones you know from the future and the conditional; here they stop telling time and start guessing.

You knowA guess
  1. Está en casa.he/she is at home
  2. Estará en casa.he/she is probably at home
  3. Quizás esté en casa.perhaps he/she is at home

The weakest step, ., takes the subjunctive: see the subjunctive of doubt.

The future: a guess about now

future: a guess about nowWhat do the colours mean?

Put a verb about the present into the future and the tense means "probably", "must" or "I wonder":

UseSpanishEnglish
the time¿ ?I wonder what time it is.
where .He/She is probably at work.
age .He/She must be about thirty.
the doorbell¿ ?Who can that be at this hour?
right now .They' probably having dinner.
Four alarm clocks in a row, with tick marks but no numbers: the first shows one o'clock, the second two o'clock, the third half past two and the fourth quarter to three. The hour hand is black and the minute hand red.
  1. .
  2. .
  3. .
  4. .

No numbers on the clocks, so every time is a guess: será la una (it must be one o'clock), serán las dos (it must be two), serán las dos y media (it must be half past two), serán las tres menos cuarto (it must be quarter to three).

The conditional: a guess about the past

future: a guess about nowconditional: a guess about the pastWhat do the colours mean?

Move the guess back in time and the future becomes the conditional:

  • serían las tres: it was probably about three (then)

  • serán las tres: it is probably about three (now)

Timeline from past to future, with now marked.

UseSpanishEnglish
the time .It was probably three when he/she arrived.
a state .She was probably tired.
age .He/She must have been about thirty then.
a crowd .There were probably about a hundred people.
no answer ; .He/She didn't answer; probably asleep.

Set the two side by side:

  • . - It's probably about three (now).
  • . - It was probably about three (then).

The conditional of probability loves a rough number with or : (about a hundred people).

Guess or real future?

future: a guess about nowconditional: a guess about the pastWhat do the colours mean?

The same form can be a guess or a real future. Ask what time the sentence is about:

Read asSpanishEnglish
a guess .He/She is probably at home now.
a real future .He/She will be at home tomorrow.
a guess .She was probably tired yesterday.
a real "would" , .With so much work, anyone would be tired.

With no time word, a future about something you cannot see right now is usually a guess: . . (He/She isn't answering. He/She is probably asleep.)

Finished actions: habrá llegado, habría salido

future: a guess about nowconditional: a guess about the pastWhat do the colours mean?

plus a past participle guesses about something already done. The future perfect looks back from now:

UseSpanishEnglish
arrived .He/She must have arrived by now.
gone ; .I can't see him; he must have left.
finished .They' probably finished already.
wondering¿ ?Could I have left the keys at home?

The conditional perfect looks back from a moment in the past:

UseSpanishEnglish
left , .When I arrived, he/she had probably left.
eaten .By then they had probably had dinner.
gone ; .He/She wasn't in; probably gone to the doctor.

A clause changes the reading: , . is "he/she would have left earlier", the unreal past. With no condition in sight and a past moment to look back from ( , ), it is a guess.

Deber de: the same guess in words

future: a guess about nowconditional: a guess about the pastdeber de: the guess in wordsWhat do the colours mean?

+ infinitive says "must" out loud, with the same meaning as the tense:

The tenseDeber deEnglish
. .It must be three.
. .He/She must be at home.
. .They must have been tired.
. .He/She must have arrived by now.

Plain , with no , is an obligation:

  • . - He/She must be at home (I reckon).
  • . - You must study more (you have to).

The RAE also accepts plain for a guess ( .), so that is not wrong. The mistake is the reverse: for an obligation.

Mistakes English speakers make

future: a guess about nowconditional: a guess about the pastWhat do the colours mean?
WrongRightWhy
. . is plural
. .a past guess takes the conditional
. .an obligation is plain

Reading ¿ ? as "what time will it be?" is the other classic slip: with no future time in sight, it is a guess about now.

What to do next

  1. Look around and guess: who is that, how old is he, what time is it? Use the future.
  2. Do the sort and the story drill below.
  3. Then the conditional for the other job of the -ía forms.

Practise: test yourself

Sort into groups

0/6

Is each form a guess about now or about the past?

Tap a word, then the group it belongs in.

Complete the story

0/4

Choose the form that makes each guess.

Where is Pablo?

Son las once y Pablo no ha llegado. ¿Dónde ? en el trabajo, o perdido el autobús. El lunes también llegó tarde: las doce cuando abrió la puerta.

Gap 1 of 4

Spot the mistake

0/3

Each sentence has one mistake. Tap it.

Pick the right one

0/5

Choose the form that makes the guess.

  1. ¿Qué hora ahora? (I wonder)

  2. Ayer no vino; enfermo. (he was probably)

  3. Salió hace una hora; ya llegado. (by now)

  4. Cuando llamé, ya cenado. (they had probably)

  5. de ser las tres. (it must be)

Translation drill

0/4

Translate into English. The tense carries the guess.

  1. ¿Qué hora será?

  2. Ellos estarán cenando.

  3. Serían las tres cuando ella llegó.

  4. Ella habrá llegado ya.

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Frequently asked questions

How does Spanish use the future tense to express probability?
It puts a verb about the present into the future, and the tense means probably: means he/she is probably at home, not will be at home. ¿ ? means I wonder what time it is. means he/she must be about thirty.
What is the difference between and for probability?
The time of the guess. guesses about now: , it is probably about three. guesses about the past: , it was probably about three. The same split runs through every verb: (he is probably tired), (he was probably tired).
What does ?
He/She must have arrived, or has probably arrived. The future perfect guesses about something already done by now: , (I can't see him, he must have left). The conditional perfect pushes the same guess further back: (he/she had probably left earlier).
What is the difference between and ?
+ infinitive is a guess: , he/she must be at home. Plain + infinitive is an obligation: , you must study. The RAE also accepts plain for a guess ( ), but for an obligation ( ) is a mistake.
How do you tell a guess from a real future?
Ask what time the sentence is about. If it is about now, with , or with no time word and nothing planned, the future is usually a guess: (he/she is probably at home now). If a future time is named, it is a real future: (he/she will be at home tomorrow).