Japanese phrase
___をどのくらい続けていますか？ ___ o do no ku ra i tsuzu ke te i ma su ka
Meaning
How long have you been doing ___?
When to use it
Asks how long an activity has been continued. It is a polite way to ask about the length of time spent on an ongoing activity.
Example dialogue
日本語の勉強をどのくらい続けていますか？ nihon go no ben kyō o do no ku ra i tsuzu ke te i ma su ka
How long have you been studying Japanese?
三か月くらいです。 san ka getsu ku ra i de su
For about three months.