I learned while living in France, starting basically from scratch. The answer to your question will depend on how you define the point at which you’ve “learned” the language. First, there’s the structural learning that has to take place: the basics of the grammar, the essential conjugations, working with genders, etc. That takes a few weeks of brute study. Then comes the important milestone at which you no longer have to mentally translate the speaker’s speech into English before understanding it; you simply understand it as it is spoken. That took me a couple of months. The next milestone would be speaking without first thinking in English and mentally translating. This took another month or so. Once this is out of the way, it becomes a matter of building vocabulary, learning idioms and acquiring the accent. This can span years. It took about 2 years before I could occasionally pass for French, and even then the illusion couldn’t hold up for long. If all you need to do is negotiate casual interchanges, you’d probably be there within 1 month. But if you want to carry on more that a superficial conversation or be able to watch TV or movies without subtitles, count on 2–3 months