LMK stands for let me know. Dictionary.com lists it as an abbreviation for those words, also written lmk, and says it comes from digital communications. People use it in texts, work chats and comments to ask for a quick reply, such as whether you can come or what you decided.
Someone ends a text with LMK, a colleague drops it into a work chat, or a customer closes an enquiry with it. If you've ever nodded along without being sure, you're in good company. LMK is one of the most practical abbreviations around, and I use it myself when I'm in a hurry. Here's what it stands for, where it turns up, how to use it at work without sounding sloppy and how to answer when someone sends it to you.
LMK spelled out in plain English
The letters stand for let me know. Dictionary.com lists it as an abbreviation for those words, also written in lowercase as lmk, and says it comes from its use in digital communications. It's a quick request: tell me when you've decided, found out or are ready.
That's the whole meaning. It has no hidden second sense in everyday chat, which makes it one of the easier abbreviations to decode. One small curiosity from Dictionary.com is that LMK was also the name of an anonymous messaging app that Snap suspended in 2022, though that has nothing to do with the abbreviation in ordinary use.
Where an LMK usually appears
- At the end of a text: I'm free Saturday, lmk if that works.
- In Slack, Teams or WhatsApp work chats, as a short follow-up request.
- In a quick email between colleagues who already know each other.
- In social media comments or direct messages, when someone is arranging something.
- In a calendar invite note, such as lmk if you can't make it.
You'll see it much more in chat than in formal letters. It saves a few keystrokes, which matters when you're typing on a phone or trying to keep a thread tidy.
LMK in a message: sample lines
These are invented examples to show the tone. None are real messages:
- Example (friend): "Dinner is at eight. LMK if you're coming."
- Example (colleague): "Draft's in the shared folder, lmk what you think."
- Example (customer): "Thanks for the quote. I'll chat to my partner and lmk."
- Example (team chat): "Ping me once the files are uploaded and I'll start. LMK if any are missing."
- Example (social comment): "Interested in the workshop, lmk the details."
Each one is a polite nudge for information. None of them is urgent, which is why LMK sounds relaxed.
Is LMK acceptable at work?
It depends on the people and the platform. Between colleagues in a chat app, it's normal. In an email to a new client, a regulator or someone senior you don't know, I'd write the words out in full. Some readers, especially people whose first language isn't English, may not recognise it, and a clear sentence never causes confusion.
| Situation | LMK fine? | Better wording if not |
|---|---|---|
| Team chat with colleagues | Yes | Not needed |
| Text to a friend | Yes | Not needed |
| First email to a client | Best avoided | Please let me know |
| Message to a senior leader | Use judgement | Could you let me know |
| Formal letter or proposal | No | Please let me know by Friday |
A good rule: copy the other person's style. If they write casually, LMK is fine. If they write formally, match them. The same thinking applies to WhatsApp Business greeting messages, where tone sets the first impression.
Shorter, clearer or more polite than LMK
If you want to avoid abbreviations, there are plenty of tidy alternatives:
- Please let me know. Polite and clear.
- Do tell me what you think. Warm and a bit British.
- Keep me posted. Casual and friendly.
- Could you confirm by Thursday? Best when you need an actual answer by a date.
- Shout if you need anything. Informal, good for friends and teams.
Notice that LMK on its own doesn't set a deadline. If you need a reply by a certain day, say so, because a vague request often gets forgotten.
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LMK for customer chats on business pages
Small businesses use chat apps all day, and LMK appears in a lot of enquiries. You don't need to copy it, but you should understand it. When a customer writes lmk, they're inviting a quick answer, so a prompt, friendly reply wins trust.
If you manage messages for a business page, my tips on Messenger tricks for business pages and these Messenger hacks will help you reply faster. If a message isn't going through, this guide to WhatsApp not sending messages covers the usual causes, and scheduling WhatsApp messages is handy when you want to send an update at a sensible hour.
Answering an LMK without overthinking it
- Reply with the information they asked for, as soon as you have it.
- If you can't answer yet, say when you can: I'll confirm tomorrow.
- For a customer, thank them and give a clear next step.
- If you don't want to take part, a polite no is better than silence.
- Mirror their tone. A casual sender doesn't need a formal essay.
The biggest LMK mistake isn't using it, it's ignoring it. The sender has handed you the next move, so a short answer keeps things going.
Frequently asked questions
What does LMK mean in a text?
LMK means let me know. It's a quick way to ask someone to tell you something, such as whether they can come or what they decided.
Is LMK rude?
No. It's friendly and casual. In a formal email to someone you don't know, writing please let me know in full sounds more polite.
What is the difference between LMK and TMK?
I couldn't confirm TMK in a dictionary I read, so I'd avoid guessing. LMK is clearly listed as let me know.
Can I use LMK in a work email?
With colleagues you know well, yes. With clients, senior leaders or people who may not know the abbreviation, write the words out.
How should I reply to LMK?
Give the answer they asked for, or say when you will. A short, friendly reply is enough.
