Around 25 million people 5 or older in the U.S. speak English less than well. What time does it take learn the language?

Beginner Level (A1-A2): A1 is complete beginner. Understand and use familiar everyday expressions and very basic phrases, communicate in a basic way if the other person speaks slowly and clearly. Time to achieve: 3-6 months of consistent study and practice. Or, between 60 and 100 hours of instruction. For example, 2 hours a day for 50 days might bring you to A2. (I did that for Spanish in 50 classes).

Intermediate Level (B1-B2): Can understand the main points of clear standard speech on familiar matters regularly encountered in work, school, leisure, etc. Can deal with most

Can describe experiences and events, dreams, hopes and ambitions and briefly give reasons and explanations for opinions and plans. 1-2 years of consistent study and practice.

Advanced Level (C1): Understand a wide range of demanding, longer texts, and recognize implicit meaning. Express oneself fluently and spontaneously without much obvious searching for expressions. Approximately 3-4 years of consistent study and practice.

Here is my blig post on the numbers and characteristics of workers in the U.S. with limited English proficiency (LEP).