How long does it take to learn a second language with an acceptable degree of fluency?

Depends on how much effort you put into it. Some people have a natural knack for picking up languages and other will struggle more. So it’s hard for me to give a certain length of time when it has to do with the individual and how much exposure to the language they can get (someone learning spanish near the american/mexico border will pick it up a lot faster than someone learning mongolian in kansas).

It depends. Most exchange students learn it within about 2 to 6 months because they have to speak it in order to do even the simplest things, such as find the bathroom or get something to eat. That is why, for example, students studying a foreign language at Princeton University eat in a commons where only that language is spoken. Once you get over the hurdle of simply being able to formulate and then utter an understandable sentence, the rest is just memorizing additional vocabulary words and idioms.

OTOH, my mother studied Spanish for 50 years without ever being really able to hold a conversation.

If you live in a place where the foreign language is spoken, it may take a little more than a year to speak, and write it fluently. It definitely also depends on how dedicated you are to learning it, specially if you are not surrounded by it. In which case I recommend to watch and listen to as many movies, podcasts, etc in that language to get your ear accustomed to it.

Doing that greatly helped me when I was learning English. I’m following the same model to learn my 3rd and 4th language. Good luck!

Edit: Let me make again enphasis on how dedicated you are to learning it, because I know people who have been living in the U.S. for over ten years and still are not able to at least understand what is being told to them. They say is because they “can’t learn it”—lies, the human brain can more than 30 languages fluently! So be serious from the beginning, or don’t even try.

I agree with what’s been said so far. It depends on your knack for languages as well as your dedication and enjoyment of learning them.

My experiences with language.. I do have a knack for English and Latin languages. I got a head start in 3rd and 4th grade, where I had French classes, but I don’t really count that because I didn’t retain much. I studied French for 3 years in American high school (private). By my junior year, I was working in the second book and had gotten to a level, at least with grammar, that I felt I had plateaued.. I had a solid grasp of the grammar functions, could conjugate just about any verb in the common (non-literary) tenses, and learning new material was a breeze. However, when I actually went and lived in France as an exchange student, I found my speaking to be well under par and my grammar was only at a 5th grade level.

My host family spoke no English and I had a constant headache for my first week due to having to listen so hard and so carefully all the time, just to understand and communicate. After that, it became easier, and by October, I still struggled with not knowing how to say things, but could effortlessly converse and had a decent vocabulary. By December, I was conversationally nearly perfect, had picked up French as the French speak it, had learned slang, etc. By the time I left in June, I was almost completely fluent and my accent was good enough to where people were surprised when they learned I was American.

So, if you’re immersed and committed, and don’t struggle with languages, you could be fluent in less than a year. With Italian, I never seem to make much progress because even though I’ve spent a good amount of time there, I’m rarely immersed in the language—I go for 1–3 months every year or two, but speak a lot of English while I’m there.

My mom, on the other hand, is not as gifted with languages as I am, and it took her like 6 years of immersion (some English, but mostly Italian) to be able to comfortably converse. After 11 years, I think she speaks Italian very well, but you definitely can tell she has an American accent. :)

It’s one of my goals to focus and start learning it for real.

It depends also on how close your new language is to your existing ones.
For example, for a Spaniard to learn Italian would be really easy, and also have an advantage to learn French. Similarly, it would be easier for a Chinese person to learn Japanese as they can transfer their knowledge of kanji.

Immersion is the best way to go. I was in Poland, in a place where they spoke practically no English/Chinese (my languages), I was communicable within a couple of weeks for basic things, but it took me a year to really hold a proper conversation, and then it was no where near perfect. But then, Polish is hard, and the focus of my trip was dancing, rather than language learning. But the weird thing was, at the airport on the way back, I kept thinking, “Why are people speaking English so fast?”.. took a while for my brain to readjust…

The operational word within your question is ACCEPTABLE.

In keeping with the above comments and in case one could spend real time in-country where the language in question is the native language and after attending a worthy intense language workshop there, one might find oneself capable of an acceptable degree of fluency in 6 weeks. Otherwise, I would say 90 to 120 days of intense study would get one close to the mark.

This is really impossible to answer with a number.

I did 3 years of German. I could not make a proper sentence for the life of me. Then I moved to Germany and within a year I was fluent enough to have any conversation with anyone. After 4 years in Germany I spoke the language well enough to get a degree in it (though I’m really bad at it and would never teach it).

It took me 5 months in Poland to be able to communicate somehow, but I already spoke some Czech and Russian.

Took me 2 years to learn Arabic (with a teacher) but I had a Lebanese girlfriend at the time, which is like cheating. I have forgotten all of it since then.

I think that generally if you spend a lot of time learning a language, and especially if you live in the country and get everyday practice, a year would suffice. As long as it’s a place where nobody speaks English. If you’re trying to learn it abroad though, it could take much longer, since you only really practice for a few hours per week. I don’t think you can ever really learn a language properly like that.

@Jack79 – Ich bin wirklich sehr beeindruckt. Lernst Du denn alle paar Jahre eine neue Sprache?

One way to help indeed is to learn as much about the culture from where the language springs. Language is a song of a people. Another good tip is, Love The People. Love The Language. Love Their Song. Learn To Sing Their Song Just Like They Do And For The Same Reaons. It really does help!

@mattbrowne nein, aber ich konnte. Ich denke dass wenn man in ein Land lebt, dann geht es viel einfacher.

I’m sure the above is full of mistakes, but you probably got what I meant. That’s what I mean about fluency.

@Jack79 – 90% perfekt!

“Nein, aber ich konnte es mal. Ich denke es geht viel einfacher wenn man in einem Land lebt (in dem diese Sprache gesprochen wird).”

At your level you would be able to reactivate your language skills within 2–3 weeks of full exposure to native speakers.