I would like to know which of the following sentences is correct.

  1. If you had come tomorrow, I might have been able to help you.​

  2. If you came tomorrow, I might be able to help you.​

4 Answers 4


The following three sentences mean different things.

If you had come tomorrow, I might have been able to help you.

This sentence is a counterfactual. It means that, because you came today instead of tomorrow, I can't help you. And there is no chance that I can help you if you come back tomorrow—you lost your chance for help by coming on the wrong day. Or maybe you have a deadline; tomorrow is too late.

If you came tomorrow, I might be able to help you.
If you come tomorrow, I might be able to help you.

These both mean that I can't help you today, but if you come tomorrow, there is a chance that I will help you.

The difference between them is in my perception of how likely it is that you will come back tomorrow. If I think it's very unlikely, I would use came. If I think it's very likely, I would use come. And for moderate likelihoods, either tense works fine.


Someone else posted an answer here that seemed sensible, then deleted it for some reason. The rules were as described in this website:


(1) real conditional:

"If" + simple present, (then) + simple future.

If you come tomorrow, I will help you.

(2) unreal conditional:

"If" + simple past, (then) + would* + base verb.

If you came tomorrow, I would help you.

note: could, should and might can all be substituted for would here, but the meaning changes slightly.

The next rule is instructive, although it doesn't relate to the question, because it must occur in the past.

(3) impossible conditional referring to past

"if" + Past Perfect, + would + have + Past Participle

If you had come yesterday, I would have helped.


Number 2 is more correct than number 1. In number 2, as the subjunctive form of come, came is considered to be "correct" usage here, but the indicative come is more often heard. "If you come tomorrow, I might be able to help you.

Regarding number 1, the introductory clause is usually said/written as "Had you come tomorrow,". In addition, the construction is generally used more in the past tense than in the future tense, because it implies a counterfactual situation. Future events are not (yet) counterfactual, so "Had you come yesterday, I might have been able to help you." is correct.

Oddly, when "if" is used for past subjunctive, the past tense came is used, e.g. "If you came yesterday, I didn't help you." For future subjunctive with "if," either come or came can be used, but I think come is more often used. i.e. "If you come tomorrow, I will help you." is heard more than "If you came tomorrow, I would help you."

https://en.m.wikipedia.org/wiki/English_subjunctive cf. "Distinguishing from past indicative after if"

Using auxiliary/helper verbs in the adverbial phrase "might be able to help" complicate things just a bit more. "Might be able to help" is the indicative, and can substitute for "will" in the example above. "Might have been able to help" is the past subjunctive case that can substitute for "would".

  • > Future events are not (yet) counterfactual But if we know that a future event is counterfactual, wouldn't use of 'if'' be incorrect? For example, I know that you will not come tomorrow, would the sentence (1) in this case be incorrect?
    – Vronsky
    Sep 18, 2016 at 9:00
  • 2
    Had you come is equivalent to If you had come, except for being somewhat old-fashioned and more formal. As a native speaker, I don't see any difference between them in meaning. Sep 18, 2016 at 14:25
  • @Peter You are right! The meanings are the same, but using 'if' pulls in a lot of grammar exceptions that have not been formally settled. .Using modal verbs like had pulls in another set, and using both sets together results in some ambiguous constructs. No one would say that "Had you came.." is correct, but whether you say "If you come..." or "If you came" on whose rules you are following. Most people would say "If you had come," rather than "If you had came," and the rule for modal verbs is the reason. Sep 18, 2016 at 15:22
  • You say "Regarding number 1, the introductory clause is usually said/written as 'Had you come tomorrow.'" I disagree – "had you come" is old-fashioned and formal, and most native English speakers would say "if you'd come." Sep 18, 2016 at 15:36
  • I somewhat agree. "Had you come tomorrow" is nonsense, because had is a past tense verb that conflicts with the future tomorrow, not because it sounds formal. "If you'd come" is useful, techically correct, but ambiguous. If you are talking about yesterday, it means "If you HAD come," but if you are talking about tomorrow, it means "If you would/could come." Sep 18, 2016 at 16:11

The first sentence is incorrect,because a counterfactual conditional is a proposition which states what would have followed had the actual sequence of events or circumstances been different. Referring to future you can use either a real conditional

If you come tomorrow,I will be able to help you.

or an unreal conditional

If you came tomorrow,I would (could,might) be able to help you

As events in the future have not happened yet, we cannot refer in the IF-clause to a counterfactual future action or state. However infinitesimal the possibility, it exists, and therefore can be presented only as a hypothetical, not as a counterfactual action or state. #53ais therefore a possible utterance, #53b is not:

53a. If the sun exploded tomorrow, the solar system would be destroyed.


53b *If the sun had exploded tomorrow, the solar system would be destroyed.

With past counterfactual situations, IF is sometimes omitted in more formal English, and subject and verb are inverted:

Had I saved more [in the past],I would retire next year.

Had Watson not bungled that interview last year, he would be the anchorman now.

Had it had been fine yesterday, we would have had a barbecue


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