Q: How long does it take to learn to play Piano like an expert?

A: That depends on how you define “expert.”

Malcolm Gladwell has written a fascinating study, "Outliers: The Story of Success" (Little, Brown & Co., 2008), in which he says it takes about 10 years, or 10,000 hours, of practice to attain true expertise, in anything. That includes piano. (10,000 hours over 10 years is 1,000 hours per year. That's about 3 hours per day, 6 days per week).

If you want to play piano for enjoyment and be a good piano player, not a world class expert, you can do that in far less time, depending on how much talent you have, how smart you are in how you spend your practice time, and how good your teacher is. For example, 1 hour of practice per day 5 days a week for 10 years with weekly lessons with a good teacher will nearly always result in a very competent proficiency.