Let me know is very similar to "tell me". We use both expressions to ask another person to inform us or give us information.
We use "tell me" when the other person already knows or has the information.
A) Do you know where Bob is?
A) Tell me.
We use "let me know" when the other person does not know the information but will know in the future. It is asking the person to inform or give information after they find out at a later time.
A) When is the show?
B) I don't know, but I will check.
A) Okay. Let me know.
We can also use "let me know" to ask about something in the future when we do not know if the person knows. This is the same as "tell me".
- Please let me know the time and date of the meeting.
Many times, we need to put more information after the word "know". We usually use noun clauses or nouns. Let me know + noun clause/noun...
- Let me know if you want to go.
- Let me know if you can't come.
- Let me know the time and place.
- Let me know if she is interested in buying the car.
- Let me know when the show starts.
- Let me know the name of the restaurant.
- Let me know what I can do to help.
We can change "me" to another pronoun.
Bonus Tips and Points
- Let her know when the meeting will start.
- Let him know if you can come.
- Let them know the password to the house, please.
- Let her know that we will not be able to attend her show.
1. We can make this sentence pattern more polite by using "please", by asking a question, or by using "please" with a question.
- Please let me know if you can come.
- Let me know what you need me to do, please.
- Can you let her know that we will be a little late?
- Could you please let me know after you find out?
- Can you let me know where the meeting will be, please?
2. There is one more sentence pattern that we should know. Person 1 + will let + Person 2 + know + noun/noun clause...
In this kind of sentence, "will let somebody know" is exactly the same as "will tell somebody".
Real-World English Conversations
- I will let you know when the show starts.
(=I will tell you when the show starts.)
- Sally will let us know if it is okay to come.
(=Sally will tell us if it is okay to come.)
A) I will let you know tomorrow when the presentation will be.
B) Let me know as soon as possible.
A) Can you let me know what I need to do?
B) I will tell you as soon as I find out.
A) I will ask and let you know later.
B) Sounds good. Let me know when you find out.
A) When is the meeting?
B) I am not sure.
A) Okay. Please let me know as soon as possible. I have to arrange my schedule for next week.
A) Are you going to the party?
B) I am not sure yet.
A) Let me know once you decide.
B) I will. Use these free English lessons to learn the most common sentence patterns in the English language. If you learn these sentence and questions well, it will help you speak English well. Study the lessons thoroughly, practice making your own sentences, and come back to review often. If you do these three steps, your English speaking will improve quickly and you will be able to have natural English conversations.