What is the difference between may and might?

They share possibility, and in many present-future guesses they are interchangeable: It may rain. It might rain. May is a little more formal and a little more willing to treat the chance as real. Might is a little more tentative, it is the past of may in reported speech (She said she might be late), and it is the form for unreal conditions and for past criticism (You might have warned us). Permission still belongs to may, not might.

Is might just the past tense of may?

Historically yes, and that is still true after said, thought, and in hypotheticals. In a guess about now or later, might is not a past tense; it is a present modal that sounds slightly remoter than may. She might be on the quay describes now. She said she might be on the quay reports a past statement.

Can I use might for permission?

Not to grant it. You might leave your case in the office reads as a suggestion. To allow something, use may (formal) or can (informal). Might I is a very polite way to ask, not to give, permission, and it is uncommon in everyday speech.

When do I use may have and might have?

Both guess about the past: She may have missed the last crossing. She might have missed the last crossing. Use might have, not may have, when you are criticising a missed action: You might have told us the causeway floods. Could have also covers that criticism and the unused option.

Which is more likely, may or might?

May can sound more likely, might less likely, but this is a tendency rather than a scale you can measure. Context, if, and stress do more work. Treat them as near-synonyms for present-future possibility, and save your precision for permission, reported speech, and might have as criticism.

English grammar · Intermediate

May vs. Might: Possibility, Permission, and Overlap

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

May and might are modal verbs of possibility, and might is also the past and hypothetical form of may. In modern English they overlap heavily for guesses about now and later (It may rain. It might rain.). The useful differences that remain are register (may is more formal), remoteness (might can sound less likely or more tentative), permission (may I is still the formal grant; might I is rare and very polite), and past speculation (may have / might have plus a participle).

We may berth tonight; we might have to wait for the next tide.

may for a real present possibility; might for a slightly remoter one

What it is

May and might both sit in front of a base verb and both colour it with uncertainty or with permission. Historically, might is the past of may, and that history still shows in reported speech (She said she might be late) and in hypotheticals. In conversation about the present and the future, the two forms have moved together: many speakers treat It may be the plumber and It might be the plumber as the same guess. What you can still teach, and still hear, is a small set of preferences: may for formal permission and for a possibility you are willing to treat as real; might for a remoter chance, a more tentative guess, and for the past of may.

You may leave your case in the office. (formal permission) You might want to leave it; the hall is crowded. (a tentative suggestion, not a grant)

How to spot it

Look for may or might plus a base verb (may berth, might wait) or plus have and a participle (may have gone, might have gone). A question with may I is almost always permission. A statement about the weather, a delay, or an identity is almost always possibility.

The crossing may be cancelled after midnight. (a real chance, slightly formal)
The crossing might be cancelled if the wind veers. (a remoter or more conditional chance)
May I leave the cello behind the desk? (formal request for permission)
She said she might join us after the preview. (might as the past of may in reported speech)

May not denies permission or possibility (You may not smoke here. It may not be the last ferry.). Might not usually denies possibility only (It might not be the last ferry.). Might not for permission is rare.

May vs. Might Quick Reference

May and might side by side

Use	May	Might
Present or future possibility	It may rain later.	It might rain later. (often a shade less likely)
Formal permission	You may wait in the hall.	Might I wait in the hall? (very tentative ask)
Reported speech / past of may	rare in this job	She said she might be late.
Hypothetical result	If the tide serves, we may berth.	If the tide served, we might berth.
Past speculation	She may have missed the crossing.	She might have missed the crossing.
Criticism of a past inaction	uncommon	You might have warned us about the roadworks.
May / might as well	We may as well stack the chairs.	We might as well stack the chairs.

Common May vs. Might Examples in English

Overlap first, then the corners where one form still does a job the other cannot:

Possibility Now and Later

That figure on the steps may be the joiner.: a present guess you are prepared to treat as plausible
That figure on the steps might be the joiner.: the same guess, often a little less committed
We may need a second crate for the scores.: a practical future possibility
We might need a second crate if the first one leaks.: the same need, tied to a condition

In everyday speech the two are often interchangeable here. If you want to sound more formal or more willing to believe the possibility, choose may. If you want more distance, choose might.

Permission

You may leave your case in the office.: a formal grant of permission
May I sit in on the last movement?: a formal request for permission
Visitors may not cross the rope.: a formal prohibition
Might I add one note about the glaze?: an extremely polite, slightly old-fashioned request

Can I is the usual informal request. May I is the form institutions still write on signs. Might I is rare outside careful politeness.

Past and Hypothetical

She said she might come after the preview.: reported speech: original words were I may come
If the wind dropped, we might still sail.: hypothetical: a remoter condition
If the wind drops, we may still sail.: real present condition: may is natural
I thought I might find a spare fuse in the drawer.: a past thought about a possibility

When the surrounding clause is past (said, thought, if the wind dropped), might is the form that fits. May in those slots sounds like a present judgement interrupting a past story.

May Have and Might Have

She may have missed the last crossing.: a present guess about a past event
She might have missed the last crossing.: the same guess, often more tentative
You might have told us the causeway floods.: criticism: you had the chance and did not take it
We may not have packed enough glaze.: a present worry about a past packing job

For a guess about the past, may have and might have are both standard. For a missed opportunity you are blaming someone for, might have (or could have) is the natural choice; may have is not used that way.

How May and Might Work

Shared modal grammar, then the few meaning splits that still matter.

Both Are True Modals

May and might have one form for every subject, take a bare infinitive, and build questions and negatives without do: May I wait? You may not wait. Might they cancel? They might not cancel. There is no mays, no mighted, and no to after either word.

Might they cancel the last crossing? They might not cancel it.

question by inversion; negative with not on the modal

One form, bare verb, no did.

Overlap Is Normal for Present Possibility

For a guess about now or later, both forms are grammatical and often synonymous. Teachers who insist that might is always less likely than may are overstating a tendency. Stress, context, and if-clauses do more to mark remoteness than the choice of modal does. Learn the tendency (may = a bit more real; might = a bit more remote) and do not treat it as a law.

It may rain before we reach the ridge. It might rain before we reach the ridge.

both are present-future possibility; the second can sound slightly less sure

Same job, small shade, not a wall.

Permission Still Prefers May

On signs, in formal speech, and in careful writing, may grants and refuses permission: You may wait here. You may not smoke. Can has taken over in conversation (Can I sit here?). Might I is a very polite question, not a grant. Might you leave your case here? is not how English gives permission.

You may wait in the hall. You may not cross the rope.

grant and prohibition, formal register

Permission: may. Conversation: can.

Might Is Still the Past of May

After a past reporting verb, may usually becomes might: I may be late becomes She said she might be late. In a past or unreal condition, might belongs in the result: If the tide served, we might berth. Keep may for a present judgement even if the story is past only when you want that interruption: He said it himself: we may still berth.

She said she might join us. If the tide served, we might berth.

reported speech, then a hypothetical result

Past frame: might. Present judgement: may.

Common Mistakes with May vs. Might

Incorrect: You might leave your case in the office. (on a permission sign)

Correct: You may leave your case in the office.

Might states a possibility or a suggestion. It does not grant permission. Signs, rules, and formal grants need may (or can in informal speech).

Incorrect: She said she may be late yesterday, when she rang.

Correct: She said she might be late.

After a past reporting verb, may usually backshifts to might. Keeping may makes the permission-or-present-guess reading leak into a past report.

Incorrect: Does he may wait in the hall?

Correct: May he wait in the hall?

May is already an auxiliary. Questions invert it with the subject. Do, does, and did never sit beside it.

Incorrect: You may have told us the causeway floods. (as a complaint)

Correct: You might have told us the causeway floods.

May have guesses about the past. The complaint that someone failed to take an available action is might have (or could have), not may have.

May Have, Might Have, and May as Well

Three patterns around the pair that learners meet early and mix up.

Guessing about the past

May have and might have plus a past participle mean it is possible that this already happened.

The letter may have gone to the old loft.: a present theory about a past event
They might have stacked the chairs already.: the same kind of theory, slightly more tentative
She may not have seen the notice.: it is possible that she did not

This is not the same as could have for a missed option. They could have taken the later crossing often means the option existed. They may have taken the later crossing means perhaps they did.

May as well and might as well

Both mean there is no better option, so we should do this. Might as well is more common in speech.

We may as well stack the chairs; nobody else is coming.: no better use of the time
We might as well wait for the next tide.: the practical remaining option
You might as well take the spare fuse with you.: a resigned suggestion

There is no meaning split worth teaching between may as well and might as well. Learn them as a chunk.

Quick Check: May vs. Might

Choose may or might (or may have / might have) for the job in brackets.

1. ___ I sit in on the last movement? (formal permission)

Answer: May

May I is the formal request

2. She said she ___ join us after the preview. (reported speech)

Answer: might

past of may after said

3. You ___ leave your case in the office. (grant, on a sign)

Answer: may

might would only suggest, not allow

4. You ___ (tell) us the causeway floods. (past criticism)

Answer: might have told

might have, not may have, for blame

5. We ___ as well wait for the next tide. (no better option)

Answer: may / might

both forms of as well are standard

May vs. Might FAQs

What is the difference between may and might?: They share possibility, and in many present-future guesses they are interchangeable: It may rain. It might rain. May is a little more formal and a little more willing to treat the chance as real. Might is a little more tentative, it is the past of may in reported speech (She said she might be late), and it is the form for unreal conditions and for past criticism (You might have warned us). Permission still belongs to may, not might.
Is might just the past tense of may?: Historically yes, and that is still true after said, thought, and in hypotheticals. In a guess about now or later, might is not a past tense; it is a present modal that sounds slightly remoter than may. She might be on the quay describes now. She said she might be on the quay reports a past statement.
Can I use might for permission?: Not to grant it. You might leave your case in the office reads as a suggestion. To allow something, use may (formal) or can (informal). Might I is a very polite way to ask, not to give, permission, and it is uncommon in everyday speech.
When do I use may have and might have?: Both guess about the past: She may have missed the last crossing. She might have missed the last crossing. Use might have, not may have, when you are criticising a missed action: You might have told us the causeway floods. Could have also covers that criticism and the unused option.
Which is more likely, may or might?: May can sound more likely, might less likely, but this is a tendency rather than a scale you can measure. Context, if, and stress do more work. Treat them as near-synonyms for present-future possibility, and save your precision for permission, reported speech, and might have as criticism.