English collapses three quite different ideas into "will," "shall," and "going to" — and then uses them almost interchangeably, so that "I'll help you," "I shall help you," and "I'm going to help you" feel like stylistic variants of one thought. Icelandic keeps them firmly apart across three verbs. munu makes a prediction — a neutral forecast of what will happen. skulu expresses the speaker's commitment — a promise when you talk about yourself, a command when you talk to someone else. ætla að states an intention — your plan. Choosing the wrong one rarely makes you unintelligible, but it makes you say something you didn't mean: ég skal koma is a vow, ég mun koma is a forecast, and ég ætla að koma is a plan. This page draws the three lines and gives you a decision table to keep them straight.
The core distinction in one sentence
munu = predict (it will turn out…); skulu = commit / command (I promise / you are to…); ætla að = intend (I'm planning to…).
The trap is that all three can translate an English "I'll come," but they make three different claims about why you're saying it will happen. munu forecasts it as an outcome; skulu puts your word or your authority behind it; ætla reports your decision. Icelandic forces you to pick which one you mean — and the performative weight of skal in particular has no clean English equivalent, because English "shall" has worn down to a near-synonym of "will."
The forms, briefly
The three behave differently in grammar, which is itself a useful tell. munu and skulu are defective preterite-present auxiliaries: they take a bare infinitive (no að) and have only a present and a past-subjunctive paradigm. ætla is an ordinary weak verb and takes að + infinitive.
| Verb | Structure | Present (ég / þú) | Past / conditional |
|---|---|---|---|
| munu |
| mun / munt | myndi (the everyday "would") |
| skulu |
| skal / skalt | skyldi ("should / was to") |
| ætla |
| ætla / ætlar | ætlaði |
So already the complement gives the game away: if there's an að before the next verb, you're using ætla; if the infinitive is bare (mun koma, skal koma), you're using munu or skulu. The full paradigms live on the munu, skulu, and ætla reference pages; here we focus on choosing between the meanings.
munu: a neutral prediction
Present munu makes a prediction — the speaker forecasts that something will be the case, without claiming to control it or to be promising anything. It is the natural choice for weather, outcomes, and considered statements about how things will go, and it carries a slightly formal, declarative register. You meet it constantly in forecasts, news, and elevated writing; in casual speech about your own plans it sounds detached.
Þetta mun ganga vel, ekki hafa áhyggjur.
This will go well, don't worry. — munu forecasts the outcome; a confident prediction about how things will turn out.
Samkvæmt spánni mun hlýna um helgina.
According to the forecast it'll get warmer over the weekend. — pure prediction; weather doesn't 'intend' anything, so munu is the only fit.
Þessi ákvörðun mun hafa afleiðingar fyrir okkur öll.
This decision will have consequences for all of us. — a weighty, declarative 'will'; munu gives it formal gravity. (newspaper / formal register)
skulu: commitment (a promise) or command
This is the verb English speakers most often misuse, because skal is a performative: by saying ég skal you are not predicting and not merely planning — you are giving your word. In the first person, ég skal + infinitive is a promise or guarantee ("I'll do it, you have my word"), markedly stronger and more personal than ég mun or ég ætla að. In the second person, þú skalt is not a forecast of what you'll do — it is a directive ("you are to, you'd better"). And við skulum is the everyday "let's." Tone decides whether þú skalt lands as warm advice or as a threat, but the commitment force is always there.
Ég skal redda þessu, engar áhyggjur.
I'll sort this out, don't worry. — skal = a personal undertaking; you're promising, not forecasting. The everyday 'leave it to me'.
Ég skal hjálpa þér að flytja á laugardaginn.
I'll help you move on Saturday. — a commitment to the listener; ég mun here would sound oddly detached, as if predicting your own behaviour.
Þú skalt fara til læknis ef þetta lagast ekki.
You should go to the doctor if this doesn't get better. — þú skalt = firm advice/directive, 'you are to go'. Stronger than the gentle ættir.
Við skulum bara panta pitsu í kvöld.
Let's just order pizza tonight. — við skulum + bare infinitive = 'let's', the hortative. One of the highest-frequency uses of skulu.
ætla að: an intention or plan
ætla að + infinitive is the everyday future of intention — your plan, your decision, what you're "going to" do. This is by far the most common of the three in ordinary conversation: when an English speaker would say "I'm going to…" or a plain "I'll…" about their own plans, an Icelander reaches for ætla að. It reports a decision you've made, without the forecast flavour of munu or the binding force of skulu.
Ég ætla að læra í kvöld, ég er með próf á morgun.
I'm going to study tonight, I have an exam tomorrow. — ætla að = a stated plan; the default 'going to' of conversation.
Við ætlum til Spánar í sumar.
We're going to Spain this summer. — ætla can stand with a destination and no second verb: 'we intend (to go) to Spain'. A plan, not a forecast.
Hvað ætlar þú að gera um helgina?
What are you going to do this weekend? — asking about someone's plans/intentions, the natural everyday question.
All three on the same 'will': a worked contrast
Take the English sentence "I'll come." It hides all three Icelandic meanings, and choosing among them changes what you're actually saying:
| Icelandic | What it really says | When you'd say it |
|---|---|---|
| Ég mun koma. | It will be the case that I come (a forecast). | formal, declarative; predicting your own attendance as an outcome |
| Ég skal koma. | I'll come — you have my word (a promise). | reassuring someone, committing yourself |
| Ég ætla að koma. | I'm planning to come (an intention). | ordinary conversation about your plans — the default |
Ég skal koma, ég lofa því.
I'll come, I promise. — skal pairs naturally with 'ég lofa' because both express commitment. A vow, not a plan.
Ég ætla að koma, ef ég kemst frá vinnunni.
I'm going to come, if I can get away from work. — a plan, hedged; this is what you'd actually say in conversation.
A decision table
| You want to express… | Use | Example |
|---|---|---|
| A neutral forecast / prediction | munu (+ bare inf.) | Það mun rigna á morgun. |
| A promise / guarantee (1st person) | skulu (+ bare inf.) | Ég skal hjálpa þér. |
| A command / firm directive (2nd person) | skulu (+ bare inf.) | Þú skalt fara strax. |
| "Let's …" (hortative) | við skulum (+ bare inf.) | Við skulum fara. |
| A plan / intention (everyday future) | ætla að (+ inf.) | Ég ætla að læra í kvöld. |
| Formal / declarative "will" | munu | Þetta mun hafa afleiðingar. |
The single most useful rule of thumb: for your own plans in conversation, use ætla að. Reserve munu for forecasts and elevated written "will," and skulu for genuine commitments and directives. If you find yourself wanting munu for a personal plan, you almost certainly want ætla að instead.
Common Mistakes
❌ Ég mun fara í ræktina eftir vinnu.
Odd — for a personal plan, use intention 'ætla að fara'. mun makes it sound like a detached forecast about yourself, not a decision you've made.
✅ Ég ætla að fara í ræktina eftir vinnu.
I'm going to go to the gym after work.
The commonest error: reaching for munu where intention is meant. munu forecasts; ætla að plans. For "I'm going to…" about yourself, use ætla að.
❌ Ég skal koma á morgun.
Wrong flavour for a neutral plan — skal makes it a vow/guarantee. If you just mean 'I plan to come', it's ég ætla að koma; for a forecast, ég mun koma.
✅ Ég ætla að koma á morgun.
I'm going to come tomorrow. (Use 'Ég skal koma' only if you genuinely mean it as a promise.)
skal is a commitment, not a neutral future. Using it for an ordinary plan overstates your sentence into a vow.
❌ Það skal rigna á morgun.
Wrong sense — the weather can't promise anything. A forecast needs the prediction verb munu: það mun rigna.
✅ Það mun rigna á morgun.
It will rain tomorrow.
skulu is commitment/command; rain doesn't undertake obligations. Forecasts take munu (or simply the present tense).
❌ Ég ætla hjálpa þér.
Missing að — ætla takes 'að' before the infinitive: ég ætla að hjálpa þér. (munu and skulu take a BARE infinitive; ætla does not.)
✅ Ég ætla að hjálpa þér.
I'm going to help you.
ætla is an ordinary verb and needs að; munu and skulu are preterite-presents that take a bare infinitive. Don't carry the bare-infinitive pattern over to ætla.
❌ Ég mun að klára þetta í kvöld.
Extra að — munu takes a BARE infinitive: ég mun klára. The 'að' belongs only with ætla.
✅ Ég mun klára þetta í kvöld.
I will finish this tonight.
The mirror error: bolting að onto munu (or skulu). These take the infinitive directly — mun klára, skal klára — never *mun að klára.
Key Takeaways
- Three verbs split English "will / shall / going to": munu = prediction, skulu = commitment/command, ætla að = intention/plan.
- munu (+ bare inf.) forecasts — weather, outcomes, formal declarative "will": það *mun rigna. Its past *myndi is the everyday "would."
- skulu (+ bare inf.) is performative: 1st person = a promise (ég *skal hjálpa þér), 2nd person = a *command (þú *skalt fara), and *við skulum = "let's." skal is stronger than English "will."
- ætla að (+ að
- inf.) states an intention/plan and is the default everyday future: ég *ætla að læra í kvöld*.
- The complement is a reliable tell: bare infinitive after munu / skulu, but að + infinitive after ætla.
- Rule of thumb: for your own plans in conversation, use ætla að; use munu only to forecast and skulu only to commit or direct.
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- Expressing the Future: munu, ætla, presentB1 — How Icelandic expresses future time despite having no inflected future tense — the bare present plus a time adverb as the default, munu + infinitive for predictions, ætla að + infinitive for intention, and verða að for obligation-tinged futures, with the munu / ætla / skulu split that carves up English 'will'.
- mega, kunna, skulu, munuB1 — Four Icelandic modals beyond geta and vilja: mega 'be allowed/may' (þú mátt fara), kunna 'know how to / might' (ég kann að synda; kann að vera 'maybe'), skulu 'shall — commitment or command' (ég skal hjálpa, þú skalt fara), and munu 'will — neutral prediction' (það mun rigna). The key nuance: skal in the 1st person is a PROMISE and in the 2nd a directive — a performative force English 'shall' has lost — while munu is a detached prediction.
- The Conditional with myndi ('would')B1 — The periphrastic conditional myndi + infinitive ('would do') — the Icelandic auxiliary that lines up most neatly with English 'would' (ég myndi fara 'I would go'). myndi is the past subjunctive of munu, used in the result clause of counterfactuals and in polite hypotheticals, but idiomatic Icelandic often prefers a BARE past subjunctive instead (ég færi over ég myndi fara), and statives strongly prefer væri/ætti/gæti — 'would be' is væri, never *myndi vera.
- munuB1 — Full paradigm of the defective future auxiliary munu 'will' — a preterite-present verb with only a present (mun/munt/mun/munum/munuð/munu) and a past subjunctive (myndi…), no supine and no participle. munu predicts ('it will rain'); its past form myndi is the everyday 'would' of conditionals. Distinguishing it from skulu (commitment/obligation) and ætla (intention) is the key to using it correctly.
- skuluB1 — Full paradigm of the defective preterite-present skulu 'shall' — present skal/skalt/skal/skulum/skuluð/skulu and past subjunctive skyldi…, with no supine and no participle. skal is a performative: in the first person it makes a promise ('I shall, you have my word'), in the second a command ('you are to'). The past skyldi is the 'should/was to' of reported obligation, and við skulum is the standard 'let's'. Distinguishing skulu (commitment) from munu (prediction) and ætla (intention) is the key to using it correctly.
- ætla (to intend / be going to)A2 — Full conjugation of the weak Class-1 verb ætla (ætla / ætlaði / ætluðu / ætlað), the everyday near-future construction ætla að + infinitive, the reflexive ætla sér, and how it differs from vilja and munu.