Future Simple for Probability

Usually, the future tense describes things that haven't happened yet. You might say Comeré más tarde (I will eat later). But in this specific context, the future tense shifts its focus. It looks at the present moment through a lens of uncertainty. When you use estará to mean "he is probably," you are distancing yourself from the fact. You are saying, "I think this is true, but don't quote me on it." It is a very common way for native speakers to sound natural. If you only use probablemente, you might sound a bit like a textbook. Using the future tense for probability makes you sound like you actually live in the language. Yes, even native speakers mess this up sometimes by overthinking it, so don't worry!

1. 1Forming this is actually quite simple. You take the entire infinitive of the verb. Then, you add the future endings. It does not matter if the verb ends in -ar, -er, or -ir. They all use the same set of endings.
2. 2Take the infinitive: hablar, comer, vivir.
3. 3Add the specific endings:
4. 4yo: -é (hablaré)
5. 5tú: -ás (hablarás)
6. 6él/ella/usted: -á (hablará)
7. 7nosotros: -emos (hablaremos)
8. 8vosotros: -éis (hablaréis)
9. 9ellos/ellas/ustedes: -án (hablarán)
10. 10Watch out for irregulars like tener (tendr-), poner (pondr-), or decir (dir-). They use these same endings but change their stems. Think of them as the "cool kids" of the grammar world who refuse to follow all the rules.

Use this when you are making a guess about the present.

• Guessing the time: ¿Qué hora es? Serán las tres. (It's probably three o'clock).
• Guessing age: ¿Cuántos años tiene ella? Tendrá veinte años. (She's probably twenty).
• Guessing location: ¿Dónde está Juan? Estará en el gimnasio. (He's likely at the gym).
• Expressing wonder: ¿Quién será a estas horas? (I wonder who it is at this hour?).

Imagine you are at a job interview. You see a candidate looking nervous. You might whisper to a colleague, Estará muy nervioso (He must be very nervous). Or imagine ordering food. You see a dish you don't recognize. You might say, ¿Qué será eso? (I wonder what that is?). It adds a layer of curiosity to your speech.

Do not use this if you are 100% certain. If you see the clock says 5:00, say Son las cinco. Using Serán las cinco would make you sound like you can't read a clock. Also, do not use this for probability in the past. If you want to say "He was probably at home yesterday," this tense won't work. You would need the Future Perfect or the Conditional for that. This specific rule is strictly for "Present Guesses." It is like a selfie; it only captures the right now.

One big mistake is using probablemente AND the future tense together. It is redundant. Pick one! Another mistake is forgetting the accent marks. In the future tense, almost every form has an accent. Without them, hablará (he will probably speak) might look like hablara (a different tense entirely). It's like forgetting to put salt in pasta water; it just doesn't work. Finally, don't use it for things that are definitely going to happen. If you have a plane ticket for tomorrow, use the normal future or ir a + infinitive.

In English, we often use "must be" or "probably is."

• English: "He must be tired."
• Spanish: Estará cansado.

You could also say A lo mejor está cansado or Quizás esté cansado. However, the future tense is much faster. It is the "express lane" of Spanish probability. While quizás requires the subjunctive (which can be a headache), the future tense is straightforward and punchy.