måste (must, have to) | Swedish Grammar

måste is the Swedish modal for necessity — "must / have to." It is unusual in two ways that an English speaker must take on board. First, it is invariable: the single form måste serves the present and, in most contexts, the past too, with var tvungen att available when you need an explicit past. There is no everyday infinitive. Second — and this is the headline — its negation is suppletive: "you don't have to" is not *du måste inte but du behöver inte. Saying måste inte for "don't have to" is the single most dangerous måste error, and this card is built around it.

Principal parts and forms

Infinitive	Present	Preteritum (past)	Supine	Imperative	Type
(none in everyday use)	måste	måste / var tvungen att	(varit tvungen att)	(none)	modal, defective & invariable

The form måste does everything: it is the present, and very often the past as well (context supplies the time). When you need to mark the past unambiguously, Swedish reaches for var tvungen att ("was forced/obliged to") — note that this construction does take att, because tvungen is an adjective, not a modal. There is no living infinitive (no *att måsta) and no supine in normal use; for the perfect you again use har varit tvungen att. After måste comes a bare infinitive, and the form never changes for person.

Jag måste gå nu, annars missar jag bussen.

I have to go now, or I'll miss the bus. måste + gå — bare infinitive, present.

Igår var jag tvungen att jobba sent.

Yesterday I had to work late. var tvungen att = the explicit past — and note 'att' DOES appear, because tvungen is an adjective.

Vi måste lämna huset före tolv.

We have to leave the house before twelve. Same invariable måste, every subject.

Use 1: necessity ("must / have to")

The core job is plain necessity — something is required, whether by circumstance, rules, or the speaker's judgement. måste is stronger than bör ("ought to") and ska ("supposed to").

Vi måste skynda oss, filmen börjar snart.

We have to hurry, the film starts soon. Necessity driven by circumstance.

Du måste visa legitimation för att komma in.

You have to show ID to get in. A rule-based requirement.

Jag måste bara säga en sak innan du går.

I just have to say one thing before you leave. Everyday, slightly emphatic necessity.

Use 2: the past — måste or var tvungen att

For past necessity, you have two routes. In a clearly past context, måste itself can stand for "had to" (Jag måste gå igår). When you want to be unambiguous — especially in writing — use var tvungen att ("was obliged to").

Jag måste gå igår innan mötet var slut.

I had to leave yesterday before the meeting was over. måste read as past, fixed by 'igår'.

Hon var tvungen att ställa in resan.

She had to cancel the trip. var tvungen att — the clear, explicit past of necessity.

Use 3: the negation switch — "don't have to" is behöver inte

Here is the trap that catches almost every English speaker. English "don't have to" removes the necessity ("you needn't, it's optional"). But Swedish du måste inte does not reliably mean that — to express plain "you don't have to / it's not necessary," Swedish switches to a different verb: du behöver inte ("you don't need to"). Use behöver inte whenever you mean the obligation is lifted.

Du behöver inte komma om du är trött.

You don't have to come if you're tired. The obligation is removed → behöver inte, NOT 'måste inte'.

Ni behöver inte betala i förväg.

You don't have to pay in advance. behöver inte = 'it's not necessary'.

Du behövde inte göra det här, men tack!

You didn't have to do this, but thank you! Past of the negation: behövde inte.

Why the switch? Negation scopes differently on the two verbs. behöver inte cleanly negates the necessity ("no need"). måste inte, by contrast, is read by many speakers as negating the action ("must not-do" → "mustn't"), or it sounds simply odd — so it is unreliable for "don't have to." Play it safe: for "don't have to," always reach for behöver inte.

💡

måste has no everyday infinitive and is invariable (present and often past are both måste; the clear past is var tvungen att). Its negation is suppletive: "don't have to" is behöver inte, never *måste inte. So necessity says du måste, but lifting it says du behöver inte — two different verbs for the two directions. This must/need-not split is the one thing to drill.

Common Mistakes

❌ Du måste inte komma om du inte vill. (meaning 'you don't have to')

Dangerous — for 'you don't have to', Swedish uses behöver inte. måste inte is unreliable and reads as 'mustn't'.

✅ Du behöver inte komma om du inte vill.

You don't have to come if you don't want to.

❌ Jag måste att gå.

Incorrect — måste is a modal; it takes a bare infinitive with no 'att'.

✅ Jag måste gå.

I have to go.

❌ Igår måstade jag jobba sent.

Incorrect — måste is invariable; there's no regular past *måstade. Use måste itself or var tvungen att.

✅ Igår var jag tvungen att jobba sent.

Yesterday I had to work late.

❌ Hon var tvungen jobba sent.

Incorrect — 'tvungen' is an adjective and needs 'att': var tvungen ATT jobba.

✅ Hon var tvungen att jobba sent.

She had to work late.

❌ Jag vill måsta gå snart. / Det är bra att måsta öva.

Incorrect — måste has no everyday infinitive (*måsta). Rephrase with vara tvungen att or behöva.

✅ Jag är tvungen att gå snart. / Det är bra att behöva öva.

I have to go soon. / It's good to have to practise.

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