你打算待多久？

Use it just like the English version. You can place it at the start of a conversation. Or use it after saying hello. If you want to be more specific, add a location. For example, 你在北京打算待多久？ (How long do you plan to stay in Beijing?). The structure is very logical. Subject + Plan + Action + Duration. No tricky verb conjugations here!

Use this when meeting a traveler at a hostel. It is perfect for catching up with a friend visiting your city. Use it at the office when a colleague from another branch visits. It works well in text messages too. It shows you are interested in their plans. It helps you coordinate hanging out later.

Do not use this with your boss if they are working. It might sound like you are rushing them out. Avoid using it in a romantic breakup context unless you want to sound cold. If someone is clearly in a hurry, skip the 'plan' part. Just ask how much time they have right now. Also, do not use it for permanent moves. For moving houses, use different verbs for 'living'.

Chinese culture values hospitality and 'host' duties. When you ask this, you are often signaling a desire to treat them. If they stay long, you might plan a big dinner. If they leave soon, you might offer a quick gift. It is a polite way to gauge your responsibilities as a local friend. People in China love talking about itineraries and food spots.

If you want to be super formal, use 您 (nín) instead of 你. For a shorter, punchier version, try 待几天？ (Stay how many days?). If you are asking about a meeting, use 多长时间 (duō cháng shíjiān) instead of 多久. You might also hear 打算住多久？ (Plan to live/stay at a hotel for how long?). Each variation changes the flavor slightly but keeps the core meaning.