þurfa (to need / have to) | Icelandic Grammar

þurfa ("to need, to have to") is one of the workhorses of everyday Icelandic — you will say ég þarf að… dozens of times a day. It belongs to the small, ancient group of preterite-present verbs (the same class as eiga, kunna, mega, vita, vilja), which means its present tense behaves like an old past tense: the singular has no ending at all. That is why "I need" is the bare þarf, not "þarfur" or "þarfar." This page covers its full paradigm, the all-important þurfa að + infinitive, the slippery negation contrast with mega, and the idiom þurfa á e-u að halda.

Conjugation

Class: preterite-present. Auxiliary: hafa — ég hef þurft "I have needed."

Principal parts
Infinitive	að þurfa
3sg present	þarf
3sg past	þurfti
Supine	þurft

Person	Present (nútíð)	Past (þátíð)
ég	þarf	þurfti
þú	þarft	þurftir
hann / hún / það	þarf	þurfti
við	þurfum	þurftum
þið	þurfið	þurftuð
þeir / þær / þau	þurfa	þurftu

Person	Present subjunctive	Past subjunctive
ég	þurfi	þyrfti
þú	þurfir	þyrftir
hann / hún / það	þurfi	þyrfti
við	þurfum	þyrftum
þið	þurfið	þyrftuð
þeir / þær / þau	þurfi	þyrftu

Non-finite & imperative
Imperative (þú)	þurf (very rare — needing is not something you command)
Imperative (þið)	þurfið (rare)
Supine	þurft
Past participle	— (no adjectival participle in normal use)

💡

Notice the vowel ladder across the four cells: singular present þarf (a), plural present þurfum (u), past þurfti (u), past subjunctive þyrfti (y). These are not random spelling changes — they are ablaut, an inherited stem-vowel alternation, not the u-umlaut you see in tölum. You simply learn the four vowels as a set: a – u – u – y.

The zero-ending singular: þarf, not "þarfur"

Because þurfa is preterite-present, its present singular carries no personal ending: ég þarf, þú þarft, hann þarf. The "you" form þarft picks up a -t (the regular 2sg marker for these verbs), but "I" and "he/she/it" are the identical bare þarf. English speakers have a built-in head start here: your modal must works exactly the same way — "I must, you must, he must," never "he musts." þurfa is must's Icelandic cousin, historically and grammatically.

Ég þarf að fara núna.

I need to go now.

Þú þarft ekki að bíða eftir mér.

You don't need to wait for me.

Hún þurfti að vinna alla helgina.

She had to work all weekend.

þurfa að + infinitive — "need to / have to"

The everyday meaning is obligation or necessity, and it is almost always built as þurfa + að + infinitive. The að is not optional: leaving it out is the single most common beginner error.

Við þurfum að kaupa mjólk á leiðinni heim.

We need to buy milk on the way home.

Þurfið þið að taka strætó eða eruð þið á bíl?

Do you (pl.) have to take the bus, or are you driving?

The negation trap: þurfa ekki vs mega ekki

This is where English collapses two opposite meanings into one and Icelandic does not. In English, "you mustn't" and "you don't have to" sound related but mean the reverse of each other — one forbids, the other releases. Icelandic keeps them cleanly apart:

þurfa ekki að = "need not / don't have to" — the obligation is lifted. You're free to skip it.
mega ekki að… actually mega ekki (no að with a bare mega) = "must not / may not" — the action is forbidden.

So þú þarft ekki að fara ("you don't have to go") and þú mátt ekki fara ("you must not go") are near-opposites. Map "must not / mayn't" onto mega ekki, and "needn't / don't have to" onto þurfa ekki.

Þú þarft ekki að borga núna — það er allt í lagi að borga seinna.

You don't have to pay now — it's fine to pay later.

Þú mátt ekki reykja hérna inni.

You must not smoke in here.

💡

A quick test: if removing the rule would make life easier for the listener ("oh good, I'm off the hook"), it's þurfa ekki. If removing it would let them do something forbidden, it's mega ekki.

þurfa + object: needing a thing

þurfa can also take a direct object — the thing needed — in the accusative (occasionally genitive in formal/older usage): ég þarf hjálp "I need help," ég þarf meiri tíma "I need more time." But the idiomatic, very common way to say "need something" is the fixed frame þurfa á e-u að halda, where the thing needed goes in the dative and is sandwiched inside á … að halda.

Ég þarf bara smá hjálp við þetta.

I just need a little help with this.

Hann þarf á hvíld að halda eftir veikindin.

He needs rest after the illness.

Common Mistakes

❌ Ég þarfa að fara.

Incorrect — þurfa is preterite-present; the 1sg present is the bare þarf, never þarfa (that's the infinitive/3pl)

✅ Ég þarf að fara.

I need to go.

❌ Ég þarf fara heim.

Incorrect — þurfa needs að before the infinitive

✅ Ég þarf að fara heim.

I need to go home.

❌ Þú þarft ekki að reykja hérna.

Incorrect if you mean 'no smoking' — this only says you're not obliged to smoke. For a ban, use mega ekki

✅ Þú mátt ekki reykja hérna.

You must not smoke here.

❌ Ég þurfti ekki gera neitt í gær — though I wished I'd had to.

Incorrect — for a softened 'would need to / would have had to', use the past subjunctive þyrfti (y), not the indicative þurfti

✅ Ég þyrfti eiginlega að hringja í hana.

I really ought to / would need to call her.

Key Takeaways

þurfa / þarf / þurfti / þurft — a preterite-present verb; the present singular is the bare þarf (no ending), like English must.
Stem-vowel ladder (ablaut): þarf (sg) – þurfum (pl) – þurfti (past) – þyrfti (past subjunctive).
Core pattern is þurfa að + infinitive = "need to / have to"; the að is obligatory.
þurfa ekki = "don't have to" (released) vs mega ekki = "must not" (forbidden) — opposite meanings.
"Need a thing" = þurfa
- accusative, or idiomatically þurfa á e-u (dat.) að halda.
Auxiliary is hafa: ég hef þurft.

Now practice Icelandic

Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.

Start learning Icelandic→