不算什么。

You usually say it right after someone thanks you. You can also use it to describe a small problem. It often follows a 'thank you' or a 'wow' from a friend. Just drop it naturally at the start of your sentence. You don't need a complex grammar structure. It stands perfectly well on its own. It is like a verbal shrug of the shoulders.

Use it when you help a friend carry heavy bags. Use it when you stay late to help a coworker. It is great for when someone praises your Chinese skills. It works perfectly when you give a small gift. Use it when you want to show you are a helpful person. It is a staple of daily social lubrication in China.

Do not use it if someone is sharing a serious tragedy. Saying 'it's nothing' to a grieving friend is very rude. Avoid it if you actually need to be paid for a service. Don't use it if you are trying to negotiate a raise. It can sound dismissive if used during a deep, emotional heart-to-heart. If someone is truly suffering, find a more empathetic phrase. Also, don't use it if you are actually trying to brag!

Chinese culture deeply values 'Modesty' or qianxu. Accepting praise too directly can sometimes feel a bit arrogant. By saying bu suan shenme, you are protecting the other person's 'face.' You are saying the favor didn't cost you much. This removes the 'debt' the other person might feel. It is a way to maintain harmony in relationships. It is the linguistic version of a humble bow.

You might hear zhe bu suan shenme. That just adds 'this' to the front. Another common one is mei shenme. That is even shorter and more casual. If you want to be extra humble, try ququ xiaoshi. That means 'just a small matter.' But for daily life, bu suan shenme is your best friend. It is simple, effective, and always polite.