Conditionals are the grammar of "what if." Every time you make a promise, give advice, issue a warning, daydream, or regret something, you're using one. Most learners memorize a single rule — "if + present, will" — and stop there, which is why they freeze the moment they need the second or third conditional and panic completely at the mixed conditional.

The fix isn't more rules. It's one idea: the further a sentence is from reality, the further the verb steps back in time. Real and always true? Present tense. Real but in the future? Present tense plus will. Imaginary now? Past tense. Imaginary in the past? Past perfect. Once that clicks, the five conditionals stop being five things to memorize and become one system.

What Is a Conditional Sentence?

A conditional sentence says that one thing depends on another. It always has two parts:

• the if-clause — the condition: "If it rains…"
• the main clause — the result: "…we'll stay in."

The two parts can go in either order. Use a comma when the if-clause comes first; leave it out when it comes second:

• If it rains, we'll stay in. (if-clause first → comma)
• We'll stay in if it rains. (main clause first → no comma)

One thing that confuses almost everyone: the tense in the if-clause is not always the time the sentence is about. "If I had a car tomorrow…" uses a past tense to talk about the future — because the tense is showing distance from reality, not time. Keep that in mind and the rest falls into place.

The Chart: All Five Conditionals at a Glance

Here's the whole system on one page, colour-coded so you can find each type quickly throughout this guide.

Zero Conditional: Things That Are Always True

The zero conditional is for situations where the result always follows the condition. Because it's always true, if can usually be swapped for when without changing the meaning.

• Scientific facts: If you heat water to 100°C, it boils.
• General truths: If you don't water plants, they die.
• Habits and routines: If I feel tired, I go to bed early.
• Instructions (imperative in the main clause): If you see a spelling mistake, correct it.
• Cause and effect: If people eat too much sugar, they gain weight.

The past zero conditional

To describe a past habit or general truth, use the past simple in both clauses: "If it rained, we stayed indoors." "If I couldn't sleep, I read a book."

First Conditional: Real Future Possibilities

The first conditional talks about a real, possible future situation and its likely result. It's the conditional of promises, warnings, offers, advice, and predictions.

• Promise: If you help me, I'll buy you lunch.
• Warning: If you touch that wire, you'll get a shock.
• Threat: If you're late again, I'll report you.
• Offer: If you need a lift, I'll drive you.
• Prediction: If the weather stays warm, the flowers will bloom early.

The biggest rule: no "will" in the if-clause

Even though the sentence is about the future, the if-clause stays in the present simple. ❌ If it will rain, I'll stay home. → ✅ If it rains, I'll stay home.

The one exception: will is allowed in the if-clause when it means willingness or is a polite request: "If you will wait here, the doctor will see you shortly." (= if you are willing to wait)

Other tenses and modals you can use

• If-clause with present continuous: If you're going out, take an umbrella.
• If-clause with present perfect: If you've finished, you can leave.
• Main clause with a modal: If you study, you might pass. / You can use my phone if yours is dead.
• Main clause with an imperative: If you see her, tell her I called.

"If" or "when"?

Use when if you're sure the event will happen, and if if it's only possible: "When I get home, I'll call you" (I'm definitely going home) vs. "If I get home early, I'll call you" (maybe I will, maybe not).

Second Conditional: Imaginary or Unlikely Situations

The second conditional talks about situations that are unreal, imaginary, or very unlikely in the present or future. The past tense here doesn't mean past time — it means "not real."

• Imaginary now: If I were taller, I'd play basketball. (I'm not taller)
• Unlikely future: If I won the lottery, I'd quit my job.
• Advice: If I were you, I'd apologize.
• Polite requests: Would it be all right if I opened the window?
• Daydreams: If we lived by the sea, we'd swim every morning.

First vs. second: it's about how likely you think it is

"Were" for every subject

In the second conditional, were is the correct form for all subjects, including I / he / she / it: "If I were you…", "If she were here…". Was is common in casual speech, but were is the standard in formal writing. This is the subjunctive mood — explained in full in our guide to the subjunctive mood.

For very hypothetical or formal statements you can also use "were to": "If you were to lose your job, what would you do?"

Third Conditional: Imagining a Different Past

The third conditional looks back at the past and imagines it going differently. Because the past can't be changed, this conditional is always unreal — the sentence tells us what actually did not happen.

• Regret: If I had known, I would have told you. (I didn't know)
• Relief: If you hadn't warned me, I would have made a huge mistake.
• Criticism: If you had listened, this wouldn't have happened.
• Excuse: If the bus hadn't been late, I wouldn't have missed the meeting.

Watch the contraction 'd — it means two different things

In spoken and informal English, 'd can be had or would. In a third conditional you'll often see both in one sentence: "If I'd known [had known], I'd have called [would have called]."

Other modals: could have / might have

• If he had left earlier, he could have caught the train. (it was possible)
• If we had asked, they might have said yes. (it was possible, not certain)

⚠️ In speech, would have sounds like "would of," and many people write it that way by mistake. It is always would have (or would've) — never "would of."

Mixed Conditionals: When Past and Present Collide

A mixed conditional isn't a new rule — it simply uses the correct tense for each clause's own time. That means the if-clause and main clause refer to different times. There are two common patterns:

More examples of each pattern:

• If she hadn't missed her flight, she would be here now. (past → present)
• If we had saved more money, we wouldn't be worried today. (past → present)
• If he were more organized, he wouldn't have lost the file. (present → past)
• If she spoke Spanish, she would have understood the guide. (present → past)

Clue words: a time word like now, today, still, or these days in the main clause is a strong sign of a mixed conditional.

Which Conditional Should I Use? Ask Yourself…

Beyond "If": Other Words That Make Conditions

Three distinctions that cause trouble

• Unless = if…not. Don't add a second negative: ❌ Unless you don't hurry, you'll be late. → ✅ Unless you hurry, you'll be late.
• In case ≠ if. "Take an umbrella in case it rains" means take it as a precaution before you know. "Take an umbrella if it rains" means only take it when it's raining. Also, after in case use the present simple, not will.
• Even if vs. even though. "Even if it rains" (it might); "Even though it's raining" (it is). See our guide to conjunctions in English for more on connecting words like these.

Modals in Conditional Sentences

Will, would, and would have are the standard result forms, but you can swap in other modals to change the meaning — from certainty to possibility, permission, or advice.

Formal Conditionals: "Had I Known…", "Were I…", "Should You…"

In formal writing you can drop if and flip the word order. The meaning is exactly the same.

This is called inversion — see our complete guide to inversion in English grammar.

Practice: Complete, Identify, or Fix

1. "If you (mix) blue and yellow, you (get) green." → mix, get (zero)
2. "If it (rain) tomorrow, we (cancel) the picnic." → rains, will cancel
3. "If I (be) you, I (accept) the offer." → were, would accept
4. "If she (study) harder, she (pass) last year's exam." → had studied, would have passed
5. "If I (win) the lottery, I (travel) the world." (unlikely) → won, would travel
6. "If he (leave) earlier, he (not miss) the bus." → had left, wouldn't have missed
7. Identify the type: "If you don't hurry, you'll miss the bus." → first
8. Identify the type: "If I had wings, I would fly to work." → second
9. Identify the type: "If people don't drink water, they get dehydrated." → zero
10. "If I (take) that job, I (live) in Paris now." → had taken, would be living (mixed)
11. Fix: "If I will see him, I will tell him." → If I see him, I'll tell him.
12. Fix: "If I would have known, I would have called." → If I had known, I would have called.
13. Fix: "Unless you don't hurry, you'll be late." → Unless you hurry, you'll be late. (or: If you don't hurry…)
14. Rewrite formally: "If I had known, I would have helped." → Had I known, I would have helped.
15. Fix: "Take an umbrella in case it will rain." → Take an umbrella in case it rains.

Frequently Asked Questions

Summary

• A conditional has an if-clause (condition) and a main clause (result); a comma follows the if-clause when it comes first.
• Core idea: the further from reality, the further the verb steps back in time.
• Zero — if + present, present: facts and habits.
• First — if + present, will + base: real future possibilities. Never will in the if-clause.
• Second — if + past, would + base: imaginary or unlikely now/future. Use were for all subjects.
• Third — if + past perfect, would have + past participle: imagined past, regrets.
• Mixed — use the tense that matches each clause's own time (past → present, or present → past).
• Unless = if…not (no double negative); in case = as a precaution; Had I known / Were I / Should you = formal versions without if.
• Never say "if I would have" or "would of" — it's had and would have.