Calorie intake varies on a few factors including age, body composition, activity, level, health status, and health goals. Estimated calorie requirements are available on WebMD. Consult with a qualified healthcare provider to help determine what weight is best for you, especially of you have any health concerns.
For pregnant women, during the first trimester, your actual caloric stay the same as previous to pregnancy but it increases in the second and third trimesters. For more, see this post.