It’s quite common for people starting out with Chinese to want to know how long it will take to learn the language.
The answer to this depends a lot on what you consider it means to have “learnt” Chinese, after all, Chinese is deep enough that there will always be something more to learn if you want to, even after decades, so really, the learning will only stop once you decide you’ve had enough and are happy with your level.
What you really need to ask is at what point will you be happy with your Chinese such that you feel you have “learnt” it, and then you can consider how long will it take to reach this target.
For me, if someone says they know Chinese, then at a minimum I would expect them to be able to do the following things:
Converse reasonably fluently with native speakers on any given general topic, and if they don’t understand something, other people in the conversation can use Chinese to explain the meaning.
Watch and understand general TV, film and other native content, perhaps not picking up on everything, e.g. certain cultural references, but for the most part being able to follow and enjoy what is going on, and be able to discuss it afterwards with others if needed.
Read and enjoy general Chinese language materials such as websites, newspapers and novels without needing to resort to a dictionary except occasionally (and when they do, a Chinese-Chinese dictionary is enough).
Send email, chat online and/or be able to write (type) about general topics entirely in Chinese.
I think the above serves as a reasonable baseline for being able to say that you know Chinese.
It’s not saying that you understand absolutely everything, or that you never have any problems or make any mistakes, but it demonstrates a level of skill that allows you to function entirely in Chinese without too much difficulty for most situations if you wanted to.
Now some people might say that and that there are plenty of native speakers who can’t read and write Chinese and therefore based on the above definition, I’m saying that they don’t know Chinese.
To this I would say that illiterate native speakers have a little bit more leeway than people who are learning Chinese as a foreign language.
Obviously I’m not going to say that an illiterate native speaker doesn’t know Chinese, but at the same time I will say that being illiterate isn’t really a desirable quality, and it prevents you from being functional in many aspects of the language (this goes for native and non-native speakers alike). So, yes, I have different standards for native speakers vs learners.
If you are illiterate in your native language, then perhaps I’d be prepared to give you a pass if you are also illiterate in Chinese. Otherwise, I see basic literacy as a core skill that I’d expect of any non-native speaker who said they know Chinese.
Definitions aside, we can now start to ask how long it would take to reach that level of Chinese.
Based on my own personal experience, and also on that of others I know (or know of) who have reached that level, I would say that if you are able to devote yourself full-time or almost full-time to your Chinese language studies, and if you work hard and have a good study methodology, then you are probably looking at around 2-3 years to reach this point. If you are unable to commit to full-time study, or if you go at a slower pace, then maybe it will take 4-5 years. If Chinese is just a casual hobby, and you only study on and off, you might not reach that level even after 10 years.
This is not to say that after 6 months or 1 year of study you won’t be able to do anything in Chinese, just that at this point you’re still far away from being able to conduct yourself in Chinese for the majority of situations you’d encounter in your daily life without running in to language related difficulties, and trying to read newspapers and books either with or without the aid of a dictionary will be a frustrating experience.
Once you can do all the things mentioned above, you will still have plenty more to learn, but at least you will have a reasonable degree of comfort in going about your life entirely in Chinese if you want to, and your language ability should not cause too much discomfort to those you are interacting with.
Learning Chinese (or at least learning it well), is a long-term endeavour that is going to be measured in years. This in turn means you should adopt appropriate learning strategies that take this into account, and prepare yourself to be in it for the long-haul.
This way, one year into your journey, when you’re still having the same basic conversations you’ve always had, and you still can’t read a book or a newspaper, you won’t decide to give up.
Learning Chinese is a marathon, not a sprint. Although there might be times where you sprint for a bit, you need to pace yourself if you want to go the distance.