Conditional sentences are part of most English books and courses. There are different types with different names and different rules. The name can sound scary, but there are just a few tips and tricks to use to become a conditional sentences expert. Below, I’ve broken these types of sentences down into categories to make it easier to decide which to use.

Things that are always true

When something is always true, we use the present simple in both halves of the sentence. For example:

• If I’m tired, I go to bed early.
• If it’s cold outside, I wear a coat.
• If he’s bored, he plays on his phone.
• If we get lost, we ask for directions.

In these sentences, we could also use when instead of if and the meaning is the same. Here are more tips on using if and when.

We can also swap all of these sentences round and the meaning stays the same. For example:

• I go to bed early if I’m tired.

Things that are possible and likely

When something could really happen in the future, we use the present simple in the if half of the sentence and will (or might or may) in the other half. For example:

• If it rains tomorrow, I’ll stay at home.
• If I miss the bus, I’ll walk.
• I’ll give her the book if I see her.
• They’ll reserve a table if they see a good restaurant.

We can’t use when in these sentences. In most cases, we can’t use if and will in the same half of the sentence. If and will don’t like each other!

Things that are unreal or unlikely

If something is not realistic or not likely to happen, we use the past simple in the if half of the sentence and would or could in the other half. Here are some examples:

• If I had a car like that, my friends would be jealous!
• We would be very angry if they lost the key.
• If I won the lottery, I would buy a boat.
• I would change the world if I were President.

Again, it’s not possible to use when in these sentences. We should keep if and would in separate sentence halves.

Were or was?

Very often when we talk about unreal or unlikely sentences, we use were instead of was, e.g.:

• If I were rich, I would buy this house.
• If I were you, I would forget about it.
• We would give him the job if he were qualified.
• I would go out if the weather were better.

When we speak, we sometimes also use was in these sentences.

How do I know what’s possible or likely?

Sometimes it’s not clear if I’m talking about something realistic or unrealistic. In the sentence I would change the world if I were President, it’s clear that this is an unlikely sentence – for most of us! The only option is to use the past simple and would to show that I don’t think this will happen.

But what about this sentence: If it rains tomorrow, I’ll stay at home? In this example, the speaker thinks it’s possible that it could rain tomorrow. But if they thought this was impossible (maybe they’ve checked the weather forecast), they could say: If it rained tomorrow, I would stay at home.

Things in the past

If we’re talking about an unreal situation past, something that didn’t happen and we’re speculating about the possible consequences, we use the past perfect in the if part of the sentence and would/could have + past participle (third form) in the other half.

• If you hadn’t told me, I wouldn’t have known.
• If they hadn’t been late, we would have finished on time.
• I would have gone on holiday if my flight hadn’t been cancelled.
• He would have bought the phone if it hadn’t been so expensive.

Here again we can only use if and not when. None of the actions in these sentences can be changed because everything is in the past.

Things in the past affecting now

It’s also possible to combine different types of if sentences to show the effect of the past on now, e.g.:

• If I had studied more, I would be better prepared.
• If you had gone to bed earlier, you wouldn’t be so tired now.
• They’d be fitter if they had done sport more often.
• He could go home early if he’d worked harder yesterday.

In the if half of the sentence we use the past perfect; in the other half we use would or could and the base form of the main verb.

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Do you have more tips for using these sentences? Or do you have any questions about this topic? I’d love to read them!