I'm afraid a lot of it will depend on your genetics, some people can just look at a treadmill and lose weight, others will have to work harder. For me personally, It took around 3 months, but I made sure that I lost weight as slow as possible in order to maintain muscle mass. If you're not worried about losing a little muscle then it would probably be quicker for you. Drop calories, do some cardio, and make sure not to starve yourself.