For + a time period: saying how long

1. Duration is the length of a period

Imagine a stretch of time. For gives its length: ten minutes, a week, several years. It does not name the date on which the period began.

For can explicitly mark duration in English: I waited for twenty minutes, We’ve been here for a month, I’ll take a room for three days. The phrase tells us the length of waiting, being here or a planned stay.

How to build it

for + duration

We waited for twenty minutes.

Twenty minutes measures the duration of waiting, rather than its starting time.

The room is available for a week.

A week is the length of the available period.

2. A number is not compulsory

After for, name an exact period or an approximate duration: a few days, about an hour, a long time. An approximate duration is still a duration.

Pay attention to the noun form: a day, an hour, two days. In an ordinary duration expression, a number greater than one needs a plural: for six months.

I've had this bag for a long time.

You do not need to know the exact number of years to use for.

The call lasted for about an hour.

About makes the amount approximate; an hour is still a time period.

We stayed for a few days.

A few days means several days, without an exact number.

3. A state from the past until now

When a state began earlier and continues now, we often use Present Perfect: have/has + past participle. For adds the duration of that state up to the present moment.

Been is the past participle of be; known is the past participle of know. For acquaintance, I’ve known… is natural, rather than I’ve been knowing…. Continuous forms are also possible for work or residence; here, simple constructions are our main guide.

Such a statement makes no promise about the future. I’ve been here for an hour describes the period up to now; the person may leave a minute later.

How to build it

subject + have/has + past participle + for + duration

subject / S: The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
V3 / past participle: The third verb form: worked, gone, seen. Used after have/has or in the passive, for example; it is not always the same as V2.

I've been in this room for an hour, and I'm still here.

The context explicitly confirms that the person is still here now.

Marta has known her neighbour for two years.

Known describes the state of acquaintance up to now; for names its duration.

4. For does not choose the verb tense

For can be used with a completed past event or a future plan. First identify the time being described, then name the duration.

Past Simple works for a stay completed in a particular past period. A plan needs an appropriate future form. For two days by itself does not force you to choose Present Perfect.

I worked at that café for six months in 2022.

A completed period is named: worked, while for still introduces the duration.

We're going to stay with friends for two nights next month.

A future plan also has a duration.

I read for twenty minutes every evening.

A habit in Present Simple: for describes the duration of each reading session.

5. For, since and ago: three different questions

For two years answers “How long?” Since May answers “Since when?”: May is the start of the period. Two years ago answers “When?”: two years in the past.

Compare the whole expression’s meaning, rather than just the presence of a number. Two years is a period; two years ago is a point two years before now. Since two years ago is therefore possible, although for two years is often simpler.

Turning a date into a duration requires a reference moment. Do not calculate a duration from “since 2020” without knowing the relevant year, month and required precision.

It's 1 June 2026. I've had this bike since 1 June 2024.

The date after since is the starting point.

I've had this bike for two years.

With the dates specified, this is the same interval expressed as a duration.

I bought this bike two years ago.

Ago names the time of purchase, rather than the duration of possession.

6. Negatives and answers to How long?

In a negative, for can measure the time during which an event has not happened: I haven’t seen… for a week means no meeting has occurred throughout that week-long period up to now. It does not mean the meeting lasted a week.

You can answer How long…? with a full sentence or briefly: For three days. The question itself usually does not need for at the beginning.

For is sometimes omitted in an ordinary positive statement: I’ve been here five years is acceptable. In this practice, when the task requests for, omitting it means missing the learning objective, rather than automatically making a grammatical error.

I haven't seen Danylo for three weeks.

The absence of meetings continues, rather than the meeting itself.

How long have you had this desk? — For six months.

The short answer gives the duration; full I’ve had it for six months is also correct.

I've been here five years.

An acceptable version without for; to practise the target construction, add for before five years.

Common mistakes

Incorrect:We have been friends since six years.

Correct:We have been friends for six years.

Six years is a duration, rather than a starting point. Change only the preposition.

Incorrect:The visit lasted for two hour.

Correct:The visit lasted for two hours.

After two in the duration expression, use plural hours.

Incorrect:I've had this phone for long time.

Correct:I've had this phone for a long time.

The fixed expression a long time needs the article a; the approximate duration itself is correct.

Incorrect:She has know him for a year.

Correct:She has known him for a year.

After has in Present Perfect, use the past participle known. For a year is already correctly formed.

Sources