Since vs For with the Present Perfect

This is one of the smallest choices in English and one of the easiest to fix. Since marks when something started — a point in time. For marks how long it has lasted — a length of time. That's the basic rule for this use.

Since = a point in time

Use since with the moment something began: a date, a time, a day, an event.

Since can introduce a starting event

Since can be followed by a date or by a whole clause that names the starting point.

For = a length of time

Use for with a duration — a number of minutes, hours, days, years.

Why the present perfect?

In this pattern, since and for describe something that started in the past and continues now — which is exactly the job of the present perfect. That's why they are very common with the present perfect.

Note: for can also appear with finished time and the past simple: "I lived in Rome for a year" (but not now). Since is most often used with the present perfect when you mean "from that point until now": "I've lived here since 2020." It can also introduce the starting event: "I've lived here since I moved in." New to this tense? See Present Perfect vs Past Simple.

Common mistakes

Using since with a length of time.

Using the present simple instead of the present perfect.

Confusing "for ages/a while" (length) with a start point. "for ages" = a long duration; a start point would need since: "since ages ago" is wrong — say "for a long time" or "for ages".

Quick exercise

Fill in since or for.

1. We've been friends ___ 2015.
2. He's been studying ___ three hours.
3. I haven't seen her ___ last summer.
4. They've lived in Berlin ___ a long time.
5. It has been raining ___ this morning.