Here's a sentence that quietly derails a lot of intermediate learners: je serai versus je serais. One letter. Almost the same sound when spoken quickly. And yet one means "I will be" and the other means "I would be," which is not a small difference when you're making plans, giving advice, or asking someone a favour.
This is one of the most common questions I get from students who've already survived passé composé and imparfait: how do futur simple and conditionnel actually differ, and why do they look so alike? Here's the answer I give in lessons, without the jargon.
The one-sentence version
Futur simple talks about what will happen: a real, expected future. Conditionnel talks about what would happen: a hypothesis, a politeness, or something depending on a condition that may or may not be true.
Je serai à Paris demain. → I will be in Paris tomorrow. (It's happening. Real future.)
Je serais à Paris si j'avais des vacances. → I would be in Paris if I had vacation. (Hypothetical. Not happening.)
Formation: they share the exact same stem
Here's the part that causes the confusion in the first place: futur simple and conditionnel are built on the same stem, always the infinitive (or an irregular version of it), and they only differ in the ending you attach.
| Futur simple: stem + present endings | Conditionnel: stem + imparfait endings |
|---|---|
| je parlerai | je parlerais |
| tu parleras | tu parlerais |
| il/elle parlera | il/elle parlerait |
| nous parlerons | nous parlerions |
| vous parlerez | vous parleriez |
| ils/elles parleront | ils/elles parleraient |
Notice the pattern: futur simple endings are almost identical to the present tense of avoir (ai, as, a, ons, ez, ont), and conditionnel endings are exactly the imparfait endings (ais, ais, ait, ions, iez, aient). If you already know those two conjugations, you already know both of these tenses. All that's left is getting the stem right.
The trap: je and tu sound almost the same in speech
Je parlerai and je parlerais are spelled differently but pronounced very close to identically in fast, natural speech, and this is exactly why native speakers themselves sometimes mix up the spelling. The safest way to check which one you mean, when writing, is to swap the subject to nous or vous in your head: the difference between -ons/-iez and -ions/-iez is much clearer, and it tells you which tense you actually intended.
Je le ferai. → Nous le ferons. (clearly futur simple)
Je le ferais si je pouvais. → Nous le ferions si nous pouvions. (clearly conditionnel)
Irregular stems: memorise these once, use them everywhere
Around fifteen common verbs use an irregular stem instead of the plain infinitive, and critically, the same irregular stem is used for both futur simple and conditionnel. Learn it once, and you've unlocked both tenses for that verb.
| Infinitive | Irregular stem | Example (futur / conditionnel) |
|---|---|---|
| être | ser- | je serai / je serais |
| avoir | aur- | j'aurai / j'aurais |
| aller | ir- | j'irai / j'irais |
| faire | fer- | je ferai / je ferais |
| venir | viendr- | je viendrai / je viendrais |
| pouvoir | pourr- | je pourrai / je pourrais |
| vouloir | voudr- | je voudrai / je voudrais |
| devoir | devr- | je devrai / je devrais |
| savoir | saur- | je saurai / je saurais |
| voir | verr- | je verrai / je verrais |
A useful shortcut: whatever the stem looks like, it always ends in -r, right before the ending. That "r" sound just before the ending is the single clearest signal, in speech, that you're hearing futur simple or conditionnel and not some other tense.
When to use futur simple
- Predictions and plans you're confident about: L'année prochaine, je déménagerai à Lyon.
- After quand, dès que, lorsque, aussitôt que when referring to the future, where English uses a present tense but French requires the future: Quand tu arriveras, appelle-moi. (When you arrive, call me. Not "when you will arrive.")
- Si + présent in the "if" clause, the result goes in futur simple: Si tu étudies, tu réussiras.
- Softened commands, especially in writing or instructions: Vous voudrez bien signer ici.
When to use conditionnel
- Politeness, this is by far the most common everyday use: Je voudrais un café, s'il vous plaît. (I would like a coffee) instead of the blunter je veux.
- Polite requests and questions: Pourriez-vous m'aider ? (Could you help me?) is dramatically softer than Pouvez-vous m'aider ?
- Hypotheticals with si + imparfait in the "if" clause: Si j'avais plus de temps, je voyagerais davantage. (If I had more time, I would travel more.)
- Advice, especially with devoir: Tu devrais te reposer. (You should rest.)
- Unconfirmed information, common in French news reporting: Le président serait arrivé à Paris ce matin. (The president reportedly arrived in Paris this morning: it's not confirmed as fact.)
The si clause rule, in one table
This single table solves most of the confusion between the two tenses, because the tense of "si" tells you exactly which tense the result needs:
| Si + … | Result clause |
|---|---|
| si + présent | futur simple → Si tu viens, on ira au cinéma. |
| si + imparfait | conditionnel présent → Si tu venais, on irait au cinéma. |
Golden rule: never put the futur simple or the conditionnel directly after "si" when it introduces the hypothesis. It always feels tempting to English speakers ("if I will go"), but French never allows it. "Si" is always followed by présent or imparfait, and the futur or conditionnel appears in the other half of the sentence.
Practice sentences to try right now
Choose futur simple or conditionnel for the verb in brackets:
- Si j'ai le temps, je (venir) ______ te voir demain.
- Si j'avais le temps, je (venir) ______ te voir plus souvent.
- (Pouvoir) ______-vous m'indiquer la gare, s'il vous plaît ?
- Quand elle (arriver) ______, préviens-moi.
- À ta place, je (ne pas faire) ______ ça.
Answers: 1. je viendrai (futur simple, si + présent). 2. je viendrais (conditionnel, si + imparfait). 3. Pourriez-vous (conditionnel: politeness). 4. elle arrivera (futur simple, after "quand" referring to the future). 5. je ne ferais pas (conditionnel: hypothetical advice).
Why this pair is worth mastering
Futur simple and conditionnel show up everywhere, from making plans to ordering politely in a café to giving advice to a friend. Mixing them up rarely makes you unintelligible, but it does change your meaning, and it's one of the fastest ways to sound more precise and natural in both speaking and writing.
The stems are the hard part, and the only real fix is repetition until they're automatic. That's exactly what structured drilling is for.