It's completely up to you. I know this isn't the answer you wanted, but the length of chapters can vary depending on the author; some authors mix it up with both long and short chapters. The book should be as long as it needs to complete the story, don't try to expand or cut down on the length of a book if you're happy with the content.
Compare your favourite author's books and their layout, decide which you prefer to read, or make notes about what you do and don't like; it'll help you decide.
Personally, I just write until I feel that my chapter is done, I don't worry about the length.