There is no magic number that works for everyone, this number will vary from person to person based on genetics, current level of fitness, average daily activity level, age, weight, etc… To figure yours out, you’ll need to figure out what your “maintenance calories” are, that is, the calories required for you to stay at your current weight based on your activity level and other variables. Whatever that number is, eat less than that to lose weight.

To get a guesstimate number to start with, you’ll want to visit a site like Nutritiondata.com
Be honest and accurate when it asks for your stats. Use that number as a starting guide for your own experimentation and remember that that number is just a guide, you will need to feel out your own actual needs which could be higher or lower than that number.

Always consult with your health care professional before dieting or when in doubt about anything regarding your health. I am not a health care professional, just a person who has experience losing weight.