I have a question about the usage of the future perfect thingy: I know that it is used to talk about a completed action before a time in future, but is it wrong to use just plain future simple in this same case?

For example, can we use

I will finish all my money by the end of the week.

instead of

I will have finished all my money by the end of the week?

Do native speakers follow this rule in their speaking?

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    There is no future tense -- simple, perfect, imperfect, continuous, passive, or any other kind -- in English. Modal auxiliary verbs such as will, may, can, should, must, or would are often used before perfect constructions, and often imply the future. There is no single rule that applies to all of them, and native speakers follow their own tastes and their own rules in their use. These individual rules are often quite different from one another, even contradictory. As you have probably already discovered. Sorry about that. Jul 2, 2013 at 20:11
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    @John I beg you to simply delete the word "tense" from all these questions. You are just confusing people. They are taught that the future construction in English uses will, and they are right. Just because they call it tense and you don’t, changes nothing. It’s still the future perfect construction, and that is what they want answered. Stop confusing people. Please.
    – tchrist
    Jul 2, 2013 at 22:34
  • I'm not responsible for what they are taught. By that logic, one should never mention evolution around certain Christians, because it might confuse them. Jul 2, 2013 at 22:40
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    @JohnLawler: That analogy is unreasonable. The debate around evolution is not merely about terminology and definitions, but about whether or not something actually happened in the past. Using one of the various acceptable definitions of the word "tense" is fine, and the one you are on a crusade against happens to be the one that is most widely used. Linguists use many different definitions. Why do you care so much about the definition of a word? You're battling windmills. Jul 3, 2013 at 0:04
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    @JohnLawler: I didn't mean to say you were burning the cities of future-tense-sayers, it was a metaphor. I'm also not forbidding you, just correcting, OK? Jul 3, 2013 at 0:58

2 Answers 2


Both are grammatical. Both are perfectly normal (though the form with have is probably less common).

They have different meanings: not in the sense that they describe different sets of circumstances, but that they look at them in different ways.

I will finish my money by the end of the week is not focussing on a time, or if it is, it is focussing on a time before the end of the week: it is looking into the future.

I will have finished my money by the end of the week is placing the viewpoint at the end of the week, when all the money has gone. It is looking into (what will then be) the past from a point in the future.

  • Thanks a lot. Some grammatical rules are very confusing, since they are not followed by the native speakers. As a result it makes it hard to realize in which situation they should be used. I would really appreciate if you inform me about any source which includes such rules.
    – roy
    Jul 4, 2013 at 13:23
  • @roy I believe you are using the term 'grammatical rules' where you should be using 'the statements some books on grammar carelessly trot out as though they were unchallengeable grammatical rules'. You often find that one author's 'rules' contradict those of another author. And more often, that they're rules of thumb rather than true rules. Feb 5, 2018 at 10:02

Both ways of speaking are grammatical, but they different in their use.

I will finish all my money by the end of the week.

Use of will often indicates a promise or decision. In this case, it could be an affirmation. Without further context, it's difficult to see what the use was.

I will have finished all my money by the end of the week.

Here the suggested meaning is evaluative, a prediction. Appears regretful. Again without context this may not be the case, but it's subtly different.

Caveat: I recognise that there are many more uses for the two including predictive qualities for future simple, but you really need context or more examples rather than simply comparing two examples of the form.

Source: Own expertise - Development editor for digital learning content.

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