There are many sizes of faucet aerator threads. You can get an idea from the picture of the thread gauge below that you will typically see at a better equipped hardware store where aerator units are sold. (In my experience typical for a USA hardware store. Your situation may vary depending upon your geographical region).

There are many sizes of faucet aerator threads. You can get an idea from the picture of the thread gauge below that you will typically see at a better equipped hardware store where aerator units are sold. (In my experience typical for a USA hardware store. Your situation may vary depending upon your geographical region).

The thread gauge above supports the following thread sizes:

1/4-18 (M)

1/4-18 (F)

3/8-18 (M)

3/8-18 (F)

1/2-27 (F)

1/2-IPS (F)

9/16-24 (M)

5/8-18 (M)

5/8-24 (M)

5/8-27 (M)

11/16-24 (M)

11/16-27 (M)

3/4-11 (F)

3/4-27 (F)

13/16-20 (M)

13/16-24 (M)

13/16-24 (F)

55/64-27 (F)

15/16-24 (M)

15/16-27 (M)

*(F) Denotes stud used to determine female thread size

*(M) Denotes tapped hole used to determine male thread size

Add in metric sizes from other parts of the world and this list is likely to grow considerably.