French grammar · Intermediate
Devoir vs. Falloir: Two Ways to Say 'Must' in French
Devoir and falloir both express obligation. Devoir has a real subject and says who is obliged: je dois partir. Falloir is impersonal and states that something is simply necessary: il faut partir. Falloir exists only in the third person singular.
Il a fallu partir tôt, donc j'ai dû annuler mon rendez-vous.
We had to leave early, so I had to cancel my appointment.
What it is
The difference is who is on the hook. Devoir attaches the obligation to a person: je dois, tu dois, elle doit. Falloir states that the obligation exists without naming anyone, using an empty il that refers to nothing at all.
Je dois travailler ce soir. Il faut travailler pour réussir. — I have to work tonight. You have to work to succeed.
How to spot it
If you can name who must do it, devoir will work. If the necessity is general, or if you want to soften it by leaving the person out, falloir is the natural choice.
- Tu dois te reposer. — You need to rest. (aimed at you)
- Il faut se reposer. — One needs to rest. (a general truth)
- Il faut que tu te reposes. — You need to rest. (aimed at you, via falloir)
- Il me faut du repos. — I need some rest. (falloir with a noun)
Falloir is one of the very few French verbs with no first or second person. There is no je faux and no nous fallons; the verb only ever appears as il faut and its tense variants.
Devoir vs. Falloir Quick Reference
Every structure the two verbs offer
| Structure | Subject | Force | Example |
|---|---|---|---|
| devoir + infinitive | a person | personal obligation | Je dois partir. — I have to leave. |
| devoir + noun | a person | to owe | Je te dois vingt euros. — I owe you twenty euros. |
| devoir (probability) | a person or thing | must be, is probably | Il doit être malade. — He must be ill. |
| il faut + infinitive | impersonal il | general necessity | Il faut réserver. — You have to book. |
| il faut que + subjunctive | impersonal il | necessity aimed at someone | Il faut que tu viennes. — You have to come. |
| il + indirect pronoun + faut + noun | impersonal il | someone needs something | Il me faut du temps. — I need time. |
| il a fallu | impersonal il | past necessity | Il a fallu attendre. — We had to wait. |
| il faudrait | impersonal il | we ought to | Il faudrait lui écrire. — We ought to write to him. |
Common Devoir vs. Falloir Examples in French
Obligation expressed from both angles:
Devoir: Naming Who Must
- Je dois rendre ce livre demain.
- I have to return this book tomorrow.
- Nous devons prévenir les voisins.
- We have to let the neighbours know.
- Elle doit passer un examen.
- She has to sit an exam.
- Vous devez signer ici.
- You need to sign here.
Devoir is the direct route. It's also the one that sounds firmest, because the obligation is pinned to a person.
Falloir: Stating the Necessity
- Il faut manger pour vivre.
- You have to eat to live.
- Il faut vraiment y aller.
- We really need to get going.
- Il ne faut pas oublier les clés.
- We mustn't forget the keys.
- Il faut du courage pour dire ça.
- It takes courage to say that.
The impersonal il is why falloir feels less confrontational: nobody has been named, so nobody is being told off.
Falloir Plus a Subjunctive
- Il faut que tu partes maintenant.
- You have to leave now.
- Il faut qu'elle finisse ce soir.
- She has to finish this evening.
- Il faudra que nous en reparlions.
- We'll have to talk about it again.
- Il fallait qu'ils soient là à huit heures.
- They had to be there at eight.
This is how falloir names a person after all, and it's extremely common in speech, often more so than devoir.
Devoir Meaning Probably
- Il doit être en réunion.
- He must be in a meeting.
- Elle a dû oublier.
- She must have forgotten.
- Ça doit coûter cher.
- That must be expensive.
- Tu dois avoir faim.
- You must be hungry.
Falloir has no equivalent use. Il faut can never mean it's probably the case.
How the Two Verbs Divide the Work
Devoir behaves like a normal verb with an extra meaning; falloir behaves like a weather verb with an obligation attached.
Falloir Has No Subject of Its Own
The il in il faut refers to nothing, exactly like the il in il pleut. That's why the verb has no other persons: there's nobody for them to agree with.
Il faut du temps pour apprendre une langue.
It takes time to learn a language.
il faut, and nothing else.
Devoir Names the Person Under Obligation
Devoir conjugates fully and takes a real subject, so the sentence says who has to act. This makes it precise, and sometimes blunt, where falloir stays diplomatically vague.
Tu dois lui parler, pas moi.
You have to talk to him, not me.
Named subject → devoir.
Il Faut Que Triggers the Subjunctive
Necessity is not a fact, so the clause after il faut que goes into the subjunctive. This is the single most common subjunctive trigger in French, and it's usually the first one learners meet.
Il faut que je fasse les courses.
I have to do the shopping.
il faut que + subjunctive.
Devoir Also Means to Owe and to Probably Be
With a noun object, devoir means owe: je te dois cinquante euros. With an infinitive it can express a confident guess rather than an obligation, and context is what separates the two.
Il doit encore de l'argent à la banque.
He still owes money to the bank.
devoir + noun = owe.
Il Me Faut Replaces Avoir Besoin De
Slip an indirect object pronoun in front of faut and the impersonal verb acquires a beneficiary. Il me faut du temps is a slightly more literary way of saying j'ai besoin de temps.
Il nous faut une réponse avant vendredi.
We need an answer before Friday.
il me / te / lui / nous faut + noun.
Common Mistakes with Devoir vs. Falloir
Incorrect: Je faut partir. — I have to leave.
Correct: Il faut que je parte. — I have to leave.
Falloir has no first person. To attach it to a subject you either use il faut que with the subjunctive, or switch verbs and say je dois partir.
Incorrect: Il faut que tu pars. — You have to leave.
Correct: Il faut que tu partes. — You have to leave.
Il faut que always takes the subjunctive, because a necessity isn't a statement of fact. Partes is the subjunctive of partir.
Incorrect: J'ai devu attendre. — I had to wait.
Correct: J'ai dû attendre. — I had to wait.
The past participle of devoir is dû, with a circumflex in the masculine singular. There is no regular participle for this verb.
Incorrect: Il faut moi du temps. — I need time.
Correct: Il me faut du temps. — I need time.
The beneficiary is an indirect object pronoun and goes before the verb: il me faut, il te faut, il nous faut. Stressed pronouns can't fill that slot.
The Two Verbs Across the Tenses
Devoir shifts meaning as it changes tense, and falloir shows just how narrow its paradigm is. Both tables are worth reading as vocabulary rather than as conjugation drills.
Devoir in the Three Tenses You Need Most
The present is an obligation, the passé composé is an obligation that was met, and the conditional softens the whole thing into advice.
| Pronoun | Present — must | Passé composé — had to | Conditional — should |
|---|---|---|---|
| je / j' | dois | ai dû | devrais |
| tu | dois | as dû | devrais |
| il / elle / on | doit | a dû | devrait |
| nous | devons | avons dû | devrions |
| vous | devez | avez dû | devriez |
| ils / elles | doivent | ont dû | devraient |
The past participle takes a circumflex in the masculine singular only, to distinguish dû from the article du. The feminine is due and the plurals are dus and dues.
Falloir Exists Only in the Third Person
There is no first or second person anywhere in this verb. The dashes are not omissions; the forms genuinely do not exist.
| Pronoun | Present | Passé composé | Imperfect | Future | Conditional |
|---|---|---|---|---|---|
| je / j' | — | — | — | — | — |
| tu | — | — | — | — | — |
| il | faut | a fallu | fallait | faudra | faudrait |
| nous | — | — | — | — | — |
| vous | — | — | — | — | — |
| ils / elles | — | — | — | — | — |
The subjunctive is qu'il faille, which turns up after conjunctions: bien qu'il faille attendre, even though we have to wait.
The Meanings Each Tense Carries
Reading the two verbs in parallel shows how English shifts its wording while French simply changes the tense.
| Pronoun | devoir | falloir |
|---|---|---|
| Present | je dois — I must | il faut — one must |
| Imperfect | je devais — I was supposed to | il fallait — we had to |
| Passé composé | j'ai dû — I had to, I must have | il a fallu — it was necessary |
| Future | je devrai — I'll have to | il faudra — we'll have to |
| Conditional | je devrais — I should | il faudrait — we ought to |
| Past conditional | j'aurais dû — I should have | il aurait fallu — we should have |
J'aurais dû and il aurait fallu are the two standard ways of expressing regret about something not done.
Falloir's Awkward Corners
The subjunctive, the negative, and a handful of idioms account for most of the remaining difficulty.
Il faut que with the subjunctive
The subordinate clause always goes into the subjunctive, whatever the tense of falloir itself. Il faut que, il fallait que, and il faudra que all behave identically.
- Il faut que tu ailles chez le médecin.
- You have to go to the doctor.
- Il faut que nous soyons à l'heure.
- We have to be on time.
- Il faudra que vous preniez rendez-vous.
- You'll have to make an appointment.
In casual speech people often drop the il: faut que tu y ailles. The subjunctive stays.
The negative reverses the strength
Il ne faut pas is not the negative of il faut. It means you must not, not you don't have to. To say something isn't necessary, French uses ce n'est pas la peine or on n'est pas obligé.
- Il ne faut pas fumer ici.
- You mustn't smoke here.
- Tu ne dois pas y aller.
- You mustn't go.
- Ce n'est pas la peine de venir.
- There's no need to come.
The same trap exists with devoir: tu ne dois pas is a prohibition, not an absence of obligation.
Idioms built on falloir
A few frozen expressions use falloir in ways that have drifted far from the idea of necessity.
- comme il faut
- properly, as one should
- Il s'en faut de peu.
- It's a close-run thing.
- Il ne faut pas exagérer.
- Let's not get carried away.
- Il lui faut tout expliquer.
- You have to explain everything to him.
Comme il faut also works as an adjective: des gens comme il faut, respectable people.
Devoir vs. Falloir FAQs
- What's the difference between je dois and il faut que je?
- Both mean I have to. Je dois attaches the obligation to you directly and sounds slightly more formal in writing. Il faut que je is extremely common in speech, and it requires the subjunctive: il faut que je fasse les courses.
- What does il a fallu mean?
- It was necessary, or we had to. It's the passé composé of falloir and describes an obligation that arose and was dealt with: il a fallu tout recommencer, we had to start the whole thing again. There's no other person available for this verb.
- Why does il faut que take the subjunctive?
- Because the clause describes something required rather than something true. French reserves the indicative for facts, so necessity, wishes, and doubts push the verb into the subjunctive. Il faut que is the most frequent trigger of all.
- Does il ne faut pas mean you don't have to?
- No, it means you must not. Il ne faut pas fumer is a prohibition. If you want to say something isn't required, French says ce n'est pas la peine, tu n'es pas obligé, or il n'est pas nécessaire de.
- How do you say I should have in French?
- J'aurais dû plus an infinitive: j'aurais dû t'appeler, I should have called you. The impersonal equivalent is il aurait fallu: il aurait fallu réserver, we should have booked.