Few rules of French grammar are as cleanly stated and as routinely violated as the rule about tense in temporal subordinate clauses. The English grammar of "when," "as soon as," "until," and "while" allows — in fact, demands — the present tense even when the action is plainly in the future: When you arrive, call me; As soon as he sees this, he'll be furious; Until I find out, I won't be able to sleep. French rejects this construction completely. In every one of those subordinate clauses, French requires the future tense. The English speaker who says Quand tu *arrives, appelle-moi — using the present where French expects quand tu *arriveras — is committing the single most common B1 grammar error in the language. This page lays out the rule, the conjunctions it applies to, the related futur antérieur for anterior actions, and the single major exception: si-clauses, which behave in exactly the opposite way.
The rule
In French, when a temporal subordinate clause refers to an event projected into the future, that clause uses the futur (or futur antérieur). Both clauses — the subordinate and the main — sit in the future together. There is no "present serves as future" shortcut as in English.
Quand il viendra, je serai là.
When he comes, I'll be there.
Dès que tu arriveras, on commencera.
As soon as you arrive, we'll start.
Aussitôt qu'il saura la vérité, il sera furieux.
As soon as he knows the truth, he'll be furious.
Lorsqu'il partira, je serai triste.
When he leaves, I'll be sad.
In every example, the English subordinate clause uses the simple present (when he comes, as soon as you arrive, as soon as he knows, when he leaves) while the French version uses the futur (viendra, arriveras, saura, partira). This is not optional. Using the present in these contexts in French sounds wrong to native speakers in the same way that When he came, I will be there sounds wrong in English: a tense mismatch.
Which conjunctions trigger this rule
The rule applies to all temporal subordinators that introduce future-time clauses:
- quand — "when"
- lorsque — "when" (formal)
- dès que — "as soon as"
- aussitôt que — "as soon as"
- tant que — "as long as"
- une fois que — "once"
- après que — "after" (classically takes the indicative; the widespread modern subjunctive after après que is a hypercorrection from avant que)
- pendant que — "while" (when describing simultaneous future events)
Une fois que tu auras compris, ce sera facile.
Once you've understood, it'll be easy.
Tant que tu seras là, je serai content.
As long as you're here, I'll be happy.
Après qu'il aura terminé, on dînera.
After he's finished, we'll have dinner.
Pendant que tu seras en vacances, je m'occuperai du chien.
While you're on vacation, I'll look after the dog.
In each case, the English subordinate is in the present (or present perfect) and the French equivalent is in the futur (or futur antérieur). The rule is mechanical: if the action of the subordinate clause is projected into the future at the moment of speaking, French requires a future tense.
Futur simple vs futur antérieur in temporal clauses
When both clauses describe future events, the choice between futur simple and futur antérieur depends on the temporal relationship between them.
Use the futur simple in the subordinate when both events are roughly simultaneous or when the order doesn't matter:
Quand tu viendras, je serai là.
When you come, I'll be there.
Dès que je le verrai, je lui dirai.
As soon as I see him, I'll tell him.
Both events sit in the future together, with no strong sense that one must be completed before the other; both verbs take the futur simple.
Use the futur antérieur in the subordinate when the subordinate-clause action must be completed before the main-clause action:
Quand j'aurai fini mes devoirs, je sortirai.
When I've finished my homework, I'll go out.
Dès que tu seras arrivé, appelle-moi.
As soon as you've arrived, call me.
Une fois qu'il aura compris la situation, il prendra une décision.
Once he's understood the situation, he'll make a decision.
Lorsqu'elle aura terminé son discours, on applaudira.
When she's finished her speech, we'll applaud.
The futur antérieur is built like the passé composé but with the auxiliary in the futur: aurai fini ("will have finished"), seras arrivé ("will have arrived"), aura compris ("will have understood"). Auxiliary choice (avoir or être) and past-participle agreement follow the same rules as the passé composé.
The English equivalent is the present perfect: when I've finished, as soon as you've arrived. But again, English permits the simple present too (when I finish, as soon as you arrive); French strongly prefers the futur antérieur whenever there is a real anteriority relation.
The si-clause exception
Now for the rule that runs in the opposite direction. Si-clauses — conditional "if" clauses — never take the futur. They take the present, even when the meaning is plainly future. This is the inverse of the quand-clause rule and is often the source of additional confusion for learners who have just internalized the quand rule.
Si tu viens, je serai content.
If you come, I'll be happy.
Si je réussis, je ferai la fête.
If I pass, I'll throw a party.
Si tu trouves les clés, dis-le moi.
If you find the keys, tell me.
The pattern is si + présent + futur (or impératif or présent) for real, possible conditions. The si-clause itself is in the présent; the main clause takes the futur (or imperative, or present, depending on the meaning). This corresponds exactly to English if + present + future: If you come, I'll be happy. The structure is parallel to English here, which is why the si rule feels less alien than the quand rule.
The deeper logic: si introduces a conditional, hypothetical clause — the speaker is not committing to whether the event will happen. The present marks this hypothetical neutrality. Quand introduces a temporal clause — the speaker treats the event as a fixture in the future timeline. The futur marks that commitment.
Si vs quand: the asymmetry
The contrast between si and quand is one of the cleanest illustrations of how a tense difference encodes a meaning difference in French.
Quand tu viendras, on mangera.
When you come, we'll eat. (You will come — it's a matter of when, not whether.)
Si tu viens, on mangera.
If you come, we'll eat. (You may or may not come.)
In quand tu viendras, the speaker presupposes that you will come. The future tense reflects the speaker's commitment to that fact. In si tu viens, the speaker leaves your coming open as a possibility. The present tense reflects that openness — the action is not anchored to the future timeline because it might not happen at all.
This is why you cannot mix the two. Si tu viendras is wrong because si never accepts the futur. Quand tu viens (when the event is in the future) is wrong because quand requires the futur for future events. The pairing of conjunction and tense encodes the speaker's stance toward the eventuality.
The full conditional system
For completeness, here is the three-type conditional system that governs si-clauses. Only Type 1 has a future meaning; Types 2 and 3 are hypothetical and counterfactual. None of them ever uses the futur or the conditional in the si-clause itself.
| Type | Si-clause | Main clause | Use |
|---|---|---|---|
| Type 1 (real) | si + présent | futur, présent, or impératif | Open conditions about the future |
| Type 2 (hypothetical) | si + imparfait | conditionnel présent | Counterfactual present or unlikely future |
| Type 3 (counterfactual past) | si + plus-que-parfait | conditionnel passé | Past condition that didn't happen |
Si j'ai le temps, je viendrai.
If I have time, I'll come. (Type 1 — real possibility)
Si j'avais le temps, je viendrais.
If I had time, I'd come. (Type 2 — hypothetical, I don't have time)
Si j'avais eu le temps, je serais venu.
If I'd had time, I'd have come. (Type 3 — counterfactual, the past did not unfold that way)
The ironclad rule across all three types: the si-clause itself never takes the futur and never takes the conditional. It takes présent (Type 1), imparfait (Type 2), or plus-que-parfait (Type 3). The futur and conditional always live in the main clause.
Why the asymmetry exists
The quand / si asymmetry has a logical foundation. Quand clauses presuppose their content — the speaker takes for granted that the event will occur and is just locating it in time. Presupposed future events are anchored to the timeline; French marks them with the futur. Si clauses, by contrast, suspend their content — the speaker is not committing to whether the event happens. The présent in a si-clause functions as a "neutral hypothetical" tense, free of any temporal anchoring.
Common Mistakes
❌ Quand tu arrives, appelle-moi.
Incorrect if the arrival is in the future — present cannot project futurity after quand.
✅ Quand tu arriveras, appelle-moi.
When you arrive, call me.
This is the canonical English-transfer error. Quand tu arrives would be correct if it meant a habitual action ("whenever you arrive, you should call me — as a general policy"), but for a single future event the futur is required.
❌ Si tu viendras, je serai content.
Incorrect — si never takes the futur.
✅ Si tu viens, je serai content.
If you come, I'll be happy.
The mirror error: applying the quand rule to si. The two conjunctions are tense-opposites in this sense.
❌ Si je viendrais, je t'appellerais.
Incorrect — si never takes the conditional either.
✅ Si je venais, je t'appellerais.
If I came, I'd call you.
A particularly hated error in French classrooms: using the conditional after si. The conditional belongs in the main clause; the si-clause uses the imparfait for hypothetical conditions. The mnemonic taught to French schoolchildren is Les "si" n'aiment pas les "rais" — "si doesn't like -rais" — meaning si-clauses don't take conditional verb forms.
❌ Quand il finit ses devoirs, il sortira.
Tense mismatch — if 'finir' is in the future and the main clause is futur, both should be futur (or use futur antérieur).
✅ Quand il aura fini ses devoirs, il sortira.
When he's finished his homework, he'll go out.
If anteriority is implied (the homework must be done first), use the futur antérieur in the subordinate. If anteriority isn't relevant, use the futur simple in the subordinate.
❌ Dès que tu as les résultats, tu m'appelles.
Acceptable in casual conversation as a near-future, but in careful French both clauses should be in the futur.
✅ Dès que tu auras les résultats, tu m'appelleras.
As soon as you have the results, you'll call me.
In casual spoken French, you may hear the present standing in for a near-future across both clauses (Dès que tu as les résultats, tu m'appelles). This is colloquial. In writing or careful speech, use the futur in both clauses.
Key takeaways
The temporal-clause-future rule is one of the highest-value rules to internalize at B1. It applies everywhere — quand, lorsque, dès que, aussitôt que, tant que, une fois que, après que, pendant que — and the principle is invariant: a clause that means future takes the futur (or futur antérieur if anterior). The single exception is the si-clause, which takes the présent for real conditions, the imparfait for hypothetical, and the plus-que-parfait for counterfactual — never the futur and never the conditional. Together these two rules — quand takes futur for future, si takes présent for real conditions — define the French treatment of conditional and temporal subordination, and they govern every sentence about future events you will ever produce.
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- Les Propositions en quand: temporal clausesB1 — Quand introduces a temporal subordinate clause and — unlike its nearest English cousin when, which sometimes triggers the subjunctive in older grammar — always takes the indicative in French. The trickier point: when the time referred to is in the future, French uses the futur, not the present, where English uses the present.
- Quand au futur: when followed by future tenseB1 — When quand introduces a clause about a future event, French requires the futur — never the present, even though English uses the present in this position. With anterior actions, French uses the futur antérieur. This is one of the highest-frequency English-transfer errors at B1 and the rule that, once internalized, transforms learners' speech.
- Si au présent: never with the future or conditionalB1 — The iron rule of si-clauses in French: si is followed by the présent (for real conditions), the imparfait (for hypotheticals), or the plus-que-parfait (for counterfactual past) — never by the futur and never by the conditionnel. This is the central French conditional rule and the one that separates B1 accuracy from a dozen common transfer errors.
- Le Futur: OverviewA1 — French has two main futures — the synthetic futur simple (je parlerai) and the analytic futur proche (je vais parler) — plus the futur antérieur (j'aurai parlé) for completed future actions. This page maps how each is built, when each is used, and how they divide up the future-time space.
- Le Futur AntérieurB1 — The future perfect of French — the 'will have done' tense. How to form it, when to use it (especially after quand, dès que, lorsque), and how it pairs with the futur simple to mark which future action finishes first.
- Le Conditionnel in Si-Clauses: Type 2, Type 3, and Mixed ConditionalsB1 — How the conditionnel pairs with the imparfait and plus-que-parfait to express counterfactual hypotheses about the present and the past — plus the mixed pattern, the universal English-speaker error to avoid, and the schoolyard rhyme that locks the rule in.