how long did you know? vs for how long do you know

The correct phrase is "How long did you know?" This is the commonly used and grammatically correct way to ask about the duration of time someone has known something or someone.

Last updated: March 25, 2024 • 917 views

how long did you know?

This phrase is correct and commonly used in English.

This phrase is used to inquire about the duration of time someone has known something or someone. It is a grammatically correct question in English.

for how long do you know

This phrase is not correct in English.

Show examples from the web [+]

We've been friends for how long and you don't know I'm puerto rican?
New lungs work, but for how long, you know?
How long do you know this already?
How long you know about this?
Tell me, how long do you know the doll?
Your woman, how long do you know her?
You know how long it took him.
Now you know how long demetri has left to live.
You know how long he's been ill.
You know how long these things can take.
You know how long a surgical scar takes to heal.
You know how long it takes you to dress.
And you know how long it takes ladies to get ready.
You know how long it's taken me to...
-You know how long the shunt...
How long did you know each other?
How long did you know Lieutenant Schonke?
How long did you know Ryker, officer Haskell?
So how long did you know Quintana?
- Professor Tellson, how long did you know the victim?

Alternatives:

For how long have you known?
How long have you known?
How long do you know?
How long have you known for?
How long have you known that?

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how long did you know? vs for how long do you know