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For or Since: What’s the Difference?

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For and since both talk about time, but they answer different questions. For tells you how long something lasts; since tells you when it started.

This guide is for A2 to B1 learners. It sets out both prepositions side by side, shows the tenses they work with, and covers the mistakes learners make most. Three exercises let you practise straight away.

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A quick video summary

For and since: the core difference

FOR is used for a specific period or duration of time. SINCE is used for the starting point of a period that continues up to now.

Look at how the same idea changes with each preposition:

Preposition What it marks Examples
for A length of time (a duration, from start to end). He has been a doctor for 10 years. / I have lived in Rome for a year.
since A starting point in time that continues to now. He has been a doctor since 2010. / I have lived in Rome since last June.
Quick test: if the word is followed by a length of time (two hours, a year), use for. If it is followed by a point in time (Monday, 2010, this morning), use since.

For describes a period from beginning to end

For works with all tenses:

  • Mary goes to sewing class for three hours every Monday. (present simple)
  • They are studying for two hours today. (present continuous)
  • He has lived in Milan for a long time. (present perfect)
  • He has been living in Paris for three months. (present perfect continuous)
Use for before a period of time, a number, or a time word: minutes, hours, days, weeks, months, years.

Since describes a point in time up to now

Since is normally used with perfect tenses:

  • He has been here since 9 am. (present perfect)
  • He has been working upstairs since he arrived. (present perfect continuous)
  • I have lived in New York since my childhood. (present perfect)
  • It has been raining since Tuesday. (present perfect continuous)
Use since before a starting point: a time, a date, or an event.

One small word changes the whole sentence. Book a free trial lesson and practise for and since with an experienced native teacher, no credit card needed.

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Common mistakes with for and since

  1. Using since for a duration. A length of time takes for: “I have studied for two hours”, not “since two hours”.
  2. Using for for a starting point. A point in time takes since: “since Monday”, not “for Monday”.
  3. Using the wrong tense with since. Since needs a perfect tense: “I have known her since 2019″, not “I know her since 2019”.
  4. Forgetting the starting point after since. You can say “I waited two hours”, but since always needs its starting point.

Practice exercises

Try these three exercises. They open in a new tab so you can keep this guide handy.

Exercise 1: choose between for and since
Exercise 2: since or for in a sentence
Exercise 3: place the time indication

Quick self-check

Complete or fix each sentence, then reveal the answers.

1. I have worked here ___ 2018.
2. We talked ___ two hours.
3. She has been ill ___ Monday.

Show answers

1. since.   2. for.   3. since.

How did that go? Getting for and since right in an exercise is a start; using them without thinking as you speak is the goal. In a free trial lesson, an experienced native teacher will help you get there.

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Frequently asked questions

What is the difference between for and since?
For is used for a length of time (“for two hours”, “for a year”). Since is used for a starting point that continues to now (“since 2010”, “since Monday”).
Do you use since with the present perfect?
Yes. Since normally goes with perfect tenses: “I have lived here since 2015”, “He has been working since 9 am.”
Can I say “since two hours”?
No. A duration takes for: “for two hours”. Use since only before a point in time, such as “since noon”.
Does for always need the present perfect?
No. For works with any tense: “I studied for an hour” (past), “I will stay for a week” (future), “I have waited for ages” (present perfect).
How do I know whether to use for or since?
Ask what follows. A period of time (two days, a month) takes for. A point in time (Tuesday, my birthday, 2020) takes since.

Key takeaways

  • Use for for a length of time: for two hours, for a year.
  • Use since for a starting point up to now: since Monday, since 2010.
  • If a duration follows, choose for; if a point in time follows, choose since.
  • Since normally needs a perfect tense; for works with any tense.
  • When in doubt, ask: how long? (for) or starting when? (since).

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Written and reviewed by the experienced native English teachers at Live English, online since 2007.