The IIFYM calculator is the perfect tool for flexible dieting. If you are unsure how long you should take to diet, or if you have a specific date range in mind for you weight loss goals, the IIFYM fat loss calculator can be super helpful. Simply enter your weight and body fat percentage in to the flexible dieting fields below. Then enter your goal body fat percentage and click submit. We will then provide you with a range of weeks that would be the least, or most amount of weeks you should IIFYM Diet for to accomplish your weight loss goal. Flexible dieting could not be any easier!!