This page covers one of the most stubborn English-transfer errors in all of Czech: what tense to use in a clause that begins with when or if and points at the future. English forces a present tense there ("When I get home, I'll call you"). Czech does no such thing — it puts a genuine future in both clauses. Getting this right instantly makes your Czech sound like the language was built for the meaning, instead of translated into it.
The core rule
When the time or condition you are describing has not happened yet, both the subordinate clause (the when/if part) and the main clause use the future tense in Czech. There is no rule that says the when/if clause must "back off" to the present, the way English requires.
Až přijdu domů, zavolám ti.
When I get home, I'll call you.
Jestli budeš mít čas, pomůžeš mi?
If you have time, will you help me?
Look closely at the first example. English says "When I get home" — a present-tense verb. Czech says Až přijdu domů — přijdu is a future ("I will arrive"). Czech refuses to lie about the timeline: the arrival is in the future, so it is marked as future. The same logic governs the second example: budeš mít is the imperfective future of mít ("you will have"), even though English drops to "if you have time."
Two ways to build the future in these clauses
Because aspect drives the Czech verb, the future in a when/if clause shows up in one of two shapes, exactly as it does in any main clause.
- Perfective verbs use what looks like a present-tense form but means the future: přijdu (I'll arrive), dočtu (I'll finish reading), zaprší (it'll start raining). See the perfective future.
- Imperfective verbs use budu
- infinitive: budu mít (I'll have), budeš pracovat (you'll be working), budeme čekat (we'll be waiting). See the imperfective future with budu.
Až to dočtu, půjdu spát.
When I finish reading this, I'll go to bed.
Jestli zaprší, zůstaneme doma.
If it rains, we'll stay home.
Až budeš v Praze, musíš mi napsat.
When you're in Prague, you have to write to me.
Notice how naturally both aspects appear. In Až to dočtu, půjdu spát both verbs are perfective futures (dočtu, půjdu). In Až budeš v Praze, the budeš is the imperfective future of být — the state of being in Prague is ongoing, so it takes budu. Czech picks the aspect by the shape of the action and then expresses it as a future; it never falls back to a present.
Až vs. když: the trap inside the trap
English uses one word, when, for two very different things: a future event ("when I arrive") and a habitual or past one ("when I arrive, I always wave" / "when I arrived"). Czech splits these. For a single future event, use až. For a general, habitual, or past event, use když.
| Meaning | Conjunction | Example |
|---|---|---|
| when (a single future event) | až | Až přijdeš, povíme si to. |
| when (habitual / general) | když | Když přijdu, vždycky uvařím čaj. |
| when (in the past) | když | Když jsem přišel, spala. |
Až přijdeš, povíme si to.
When you come, we'll talk it over.
Když přijdu domů, vždycky si uvařím čaj.
When(ever) I come home, I always make myself tea.
The difference is real and audible to a native ear. Až přijdeš announces one specific arrival that lies ahead. Když přijdu describes a recurring habit, so it pairs with vždycky ("always"). Using když for a single future appointment sounds off, and using až for a habit is simply wrong. This page has a dedicated companion that drills the three-way split: see až vs. když vs. jestli.
Jestli, pokud: real conditions in the future
For real (open) conditions — things that genuinely might or might not happen — Czech uses jestli or the slightly more formal pokud ("if"), and again the verb is a real future.
Jestli budeš chtít, můžeme jít do kina.
If you want to, we can go to the cinema.
Pokud se nevrátí do osmi, zavoláme jí.
If she's not back by eight, we'll call her.
These open conditions are different from the kdyby conditional, which handles hypothetical or unreal situations ("if I were rich…"). Do not reach for kdyby + a conditional verb here. A real, future-possible condition takes jestli/pokud + a plain future, just like the až clauses above. For the contrast with hypotheticals, see kdyby conditional clauses.
Jestli stihneme vlak, budeme tam v poledne.
If we catch the train, we'll be there at noon.
Why Czech works this way
English grammaticalized a quirk: after when, if, as soon as, until, and before, it bans the future and substitutes the present, even though the meaning is future ("I'll wait until you finish"). This is a syntactic rule of English, not a fact about time. Czech took the more transparent path — it marks future time as future, full stop, no matter what conjunction sits in front of it. So the Czech sentence is, if anything, more logical than its English translation. The hard part for an English speaker is unlearning the reflex to drop to the present.
Common mistakes
The single biggest error is importing the English present into the Czech when/if clause.
❌ Až přijdu domů, zavolal jsem ti.
Incorrect — main clause is past, but the action is future.
✅ Až přijdu domů, zavolám ti.
When I get home, I'll call you.
❌ Jestli máš čas, pomůžeš mi?
Incorrect — uses the present 'máš' for a future condition.
✅ Jestli budeš mít čas, pomůžeš mi?
If you have time, will you help me?
The second pair is the textbook English-transfer slip. Jestli máš čas would mean "if you have time (right now, generally)"; for a future favour you need the future budeš mít.
❌ Když přijdeš zítra, půjdeme do kina.
Incorrect — 'když' for a single future event; should be 'až'.
✅ Až přijdeš zítra, půjdeme do kina.
When you come tomorrow, we'll go to the cinema.
❌ Pokud bude pršet, zůstanem doma a nebudeme šli ven.
Incorrect — 'nebudeme šli' is not a Czech form.
✅ Pokud bude pršet, zůstaneme doma a nepůjdeme ven.
If it rains, we'll stay home and won't go out.
That last error is an aspect-and-future tangle: there is no budeme + past participle future. Imperfective futures are budu + infinitive (nebudeme chodit), and the perfective future of jít is půjdeme / nepůjdeme.
Key takeaways
- After až, jestli, and pokud, Czech uses a real future — never an English-style present.
- Both clauses are usually future: Až to dočtu, půjdu spát.
- až = a single future "when"; když = habitual/general/past "when."
- Real future conditions take jestli/pokud
- future, not the hypothetical kdyby.
- The verb's aspect decides the shape: perfective present-as-future (přijdu) or budu
- infinitive (budu mít).
Now practice Czech
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Czech→Related Topics
- Temporal Conjunctions: když, až, jakmileB1 — Choosing the right 'when' for past habit, future, and the moment something happens.
- Choosing až, když, or jestliB1 — When, whenever, and if — three conjunctions English speakers confuse.
- jestli, zda, and -li: 'whether/if'B1 — Three ways to introduce an indirect yes/no question.
- The Perfective Future (= perfective present)B1 — How the perfective present form expresses a completed future action.
- The Imperfective Future (budu + infinitive)A2 — How Czech builds the future of imperfective verbs with budu + an infinitive, why it pairs only with imperfectives, and when to use it instead of the perfective.
- Aspect in the Future TenseB1 — The two Czech futures, which aspect each one uses, and why budu + perfective is impossible.