We use both since and for to say how long something has been happening:
I’ve been waiting for you since 8 o’clock.
I’ve been  waiting for you for two hours.
We use “since” when we say the beginning of the period (8 o’clock).
We use “for” when we say the period of time (two hours).

Since	For
8 o’clock 1977 Monday Christmas 12 may lunchtime April we arrived	two hours a week ten minutes five years three days a longtime six months ages

She’s been working  here since April. (= from April until now)
She’s been  working  here for six months. (not  ‘since six months ‘)
I haven’t seen Tom since Monday . (= from Monday  until now)
I haven’t seen Tom  for three day. (not ‘since three days ‘)

 

We do not use “for” in expressions with all (all day / all morning / all week / all my life etc.) See the following examples :

1. I’ve lived here all my life .(not ‘for all my life’)
2. I’ve been waiting for you all day. (not ‘for all day’)

Note the structure How long is it since …?
A: How long is it since you had a holiday ?
B : it’s been two years since  I had a holiday . (= I haven’t had a holiday for two years.)
It’s ages since Tom visited us. (= He hasn’t visited us for ages. )

Since and For Exercise

Exercise I

Complete the sentences below with since, for  or nothing (-)!

1. It’s  been  snowing…………. I got up this morning.
2. Tom’s father has been a doctor ……….. 20 years.
3. Have  you been learning English ………….. a long time ?
4.  …….. Christmas, the weather has been quite mild.
5. Ann has been on holiday ………… five days.
6. That ‘s a very old bike. I’ve had it ……… ages.
7. I have been living here ….. all my life.
8. My sister has been married …..I was seven.
9. John has been waiting for Nancy ….. two hours.
10. He has been the president of this country ………..the pandemic began.

Answers

Exercise I

1. It’s  been  snowing since I got up this morning.
2. Tom’s father has been a doctor for 20 years.
3. Have  you been learning English for a long time ?
4.  Since Christmas, the weather has been quite mild.
5. Ann has been on holiday for five days.
6. That ‘s a very old bike. I’ve had it for ages.
7. I have been living here – all my life.
8. My sister has been married since I was seven.
9. John has been waiting for Nancy for  two hours.
10. He has been the president of this country since the pandemic began.

Download the exercise here.