Female: 20 lacto vegetarian - how many calories should be taken in when dieting? when not dieting?

You should not go below 1200 calories a day when dieting. In general daily calorie needs for women ar around 1800-2000 calories. How many calories you should be taking in to maintain your weight depend on a few factors such as your height and daily activity level. You could google "daily calorie needs" and the calculators on those websites can help you to estimate your daily calorie need to maintain your current weight based on your height and activity level. If you want to lose weight you will need to either reduce the number of calories you take in (without going under 1200 calories) or increase your activity level or both. Best wishes.