First Conditional
Learn how the first conditional pairs the present simple with “will” to describe realistic, possible situations in the future.
A real possibility
The first conditional describes a realistic future situation.
The first conditional is used for situations that are genuinely possible in the future. It follows the pattern if + present simple, will + base verb.
In the sentence If it rains, we will stay inside., the condition is realistic, and the result describes what will genuinely happen if it occurs.
This sets the first conditional apart from the zero conditional, where the result is a certainty rather than a possibility, and from the second conditional, where the condition is unlikely or imaginary.
Before you begin
The first conditional is one pattern within conditionals.
This lesson focuses on the first conditional specifically. For an introduction to conditional sentences as a whole, and how the parts of a conditional sentence are identified, begin with Understanding Conditionals.
The pattern
The if-clause uses the present simple; the main clause uses “will.”
Compare the two parts of a first conditional sentence.
01
The If-Clause
If + present simple.
If it rains,
02
The Main Clause
Will + base verb.
we will stay inside.
The present simple in the if-clause does not refer to now.
Even though the if-clause uses the present simple, the whole sentence is about the future. The present simple form is simply the pattern English uses inside a first conditional if-clause.
Other modal verbs can replace will
The main clause can use a different modal verb, depending on certainty.
Can, for permission or ability
If you finish early, you can leave.
Might or could, for a less certain result
If the weather improves, we might go for a walk.
Might and could suggest the result is possible but not guaranteed, even if the condition is met.
Should, for advice or recommendation
If you feel unwell, you should see a doctor.
An imperative, for an instruction
If you see James, tell him to call me.
The main clause can also be an instruction rather than a statement with a modal verb, while the if-clause still follows the same pattern.
Word order and punctuation
The if-clause can come first or second, but punctuation changes.
If-clause first: use a comma
If it rains, we will stay inside.
If-clause second: no comma
We will stay inside if it rains.
Both orders are correct and mean the same thing.
A useful decision guide
Ask how realistic the future situation is.
01
Is this a genuine possibility for the future?
Use the first conditional: present simple, will plus base verb.
02
Does the result depend on how certain it is?
Replace will with can, might, could or should as needed.
03
Is the condition unlikely or purely imaginary?
Use the second conditional instead, with the past simple and would.
Common mistakes
Do not use “will” in the if-clause.
Using will in the if-clause.
Not: If it will rain, we will stay inside.
Correct: If it rains, we will stay inside.
Will belongs in the main clause, not the if-clause, in the first conditional.
Mixing first and second conditional forms.
Not: If it rains, we would stay inside.
Correct: If it rains, we will stay inside.
The present simple if-clause pairs with will, not would, in the first conditional.
Using the present continuous instead of the present simple.
Not: If it is raining, we will stay inside.
Correct: If it rains, we will stay inside.
The if-clause of the first conditional uses the present simple, not the present continuous.
Check your understanding
Is the first conditional used correctly?
Choose the correct answer for each sentence.
Which sentence correctly uses the first conditional?
✅ Exactly! The if-clause uses the present simple, not “will.”
❎ Not quite. Check where “will” belongs in this pattern.
“Will” only appears once, in the main clause.
“If you finish early, you can leave.” What does “can” express here?
✅ Exactly! “Can” replaces “will” to express permission in this first conditional sentence.
❎ Not quite. Look at what “can” is doing in the main clause.
Which sentence correctly uses the first conditional?
✅ Exactly! The present simple if-clause pairs with “will,” not “would.”
❎ Not quite. “Would” belongs to a different conditional pattern.
“If the weather improves, we might go for a walk.” What does “might” suggest?
✅ Exactly! “Might” softens the certainty of the result, compared with “will.”
❎ Not quite. Compare “might” with “will” in terms of how certain the result sounds.
Choose the best explanation
Select the sentence that explains the first conditional correctly.
Why is “If it rains, we will stay inside” correct rather than “If it will rain, we will stay inside”?
✅ Exactly! The if-clause stays in the present simple, and “will” stays in the main clause only.
❎ Not quite. Think about where “will” is allowed to appear in this pattern.
Why might a speaker choose “might” instead of “will” in a first conditional sentence?
✅ Exactly! The choice of modal verb reflects how certain the speaker is about the result.
❎ Not quite. Compare the certainty of “will” with the certainty of “might.”
Why does “If it rains, we will stay inside” differ from “If you heat water, it boils”?
✅ Exactly! This is the difference between the first conditional and the zero conditional.
❎ Not quite. Compare how certain each result is.
Try it another way
Complete each first conditional sentence.
Type the correct form of the verb shown in brackets.
✅ Exactly! “Will” plus the base verb forms the main clause of the first conditional.
❎ Not quite. Use “will” plus the base form of “stay.”
✅ Exactly! The if-clause uses the present simple form of “finish.”
❎ Not quite. Use the present simple form of “finish.”
✅ Exactly! “Should” replaces “will” to give advice in the main clause.
❎ Not quite. Use “should” plus the base form of “see” to give advice.
Edit the sentence
Rewrite each sentence with the correct first conditional form.
Use the note in brackets to decide what needs to change.
If it will rain, we will stay inside. (correct the if-clause)
✅ Exactly! The if-clause uses the present simple, not “will.”
❎ Not quite. Replace “will rain” with the present simple “rains.”
If it rains, we would stay inside. (correct the main clause)
✅ Exactly! The first conditional pairs the present simple if-clause with “will.”
❎ Not quite. Replace “would” with “will” to match the first conditional.
If the weather improves, we will maybe go for a walk. (rewrite using “might”)
✅ Exactly! “Might” replaces “will maybe” to express the same, less certain result.
❎ Not quite. Replace “will maybe go” with “might go.”
Quick review
The first conditional pairs the present simple with “will.”
The first conditional follows the pattern if + present simple, will plus base verb.
It describes realistic, possible situations in the future.
Can, might, could and should can replace will, depending on how certain the result is.
The if-clause never uses “will”; it stays in the present simple.
An if-clause first needs a comma; an if-clause second does not.
Remember
Ask whether the future situation is genuinely possible.
The first conditional is reserved for conditions that could realistically happen. Once that possibility is confirmed, the present simple belongs in the if-clause, and “will,” or another modal verb matching the certainty of the result, belongs in the main clause.