There is a LOT of information on the web about nutrition, what to eat/not eat, how many calories, etc. Between social media, nutrition coaches/trainers, and online google searches, it's nothing short of overwhelming when you're trying to decipher and figure out "how many calories should I be eating?!"
There are a couple different ways to figure out and determine your TDEE. Your TDEE (Total Daily Energy Expenditure) is the total amount of calories your body needs in order to maintain your current weight (aka maintenance calories). Your TDEE is composed of 4 components: BMR (Basal Metabolic Rate), NEAT (Non-Exercise Activity Thermogenesis), TEF (Thermic Effect of Food), and AF (Activity Factor). It's important to know that your body burns calories 24 hours a day, 7 days a week - not just when you're exercising. We burn calories when we blink, breathe, walk, run errands; our bodies burn calories, or "energy, even when we're consuming foods by process of digestion and absorption of macro and micronutrients (aka thermic effect of food).
Figuring out your TDEE can be determined a couple different ways. The first way is to do a simple google search of TDEE calculators. Just know there are several TDEE calculators online and none of them are perfect. The majority of online calculators will take into account your personal stats, like weight, age, height and activity factor but it's really important to understand that no matter which calculation you use, they are all estimates. There is no perfect calorie or macro calculator out there. I personally use and recommend the Mifflin St. Jeor calculator but you could also take the average of 2-3 different calculations and use that number to determine your TDEE. The second way to determine your maintenance calories is by keeping an accurate log of your dietary intake, along with daily weigh ins and see how your weigh fluctuates. I would recommend doing this for at least 2-3 weeks, taking the average of your weekly weigh ins and seeing the changes (weight gain, weight loss or weight maintenance) over the course of that 2-3 week period. How your weight responds will help you determine if you are currently eating below, at, or above your body maintenance calories. From there, you'll have a better gauge and a better idea of how many calories you should be eating.
ON A SIDE NOTE: In my 3 years + of nutrition coaching, I've had several conversations with women about their previous dieting history and years of yo-yo dieting. They've often spent months, even years of restrictive eating and have gotten to the place where their body now maintains its weight on very low calories. Only to question why they can no longer lose weight, or at the very least, realize how much harder it seems to lose that weight every time they try to diet again. It is possible for your body to get accustomed to the low calories you've been feeding it (aka metabolic adaptation). If this person were to calculate their TDEE (let's say their predicted maintenance calculated out to be 1,900 calories - which theoretically they should be maintaining their weight on), but they've spent years of dieting and restrictive eating, so now their body is now maintaining its weight on just 1,200 calories. This can be stressful for this person and problematic when deciding what their next steps are. In this persons case, I would highly recommend implementing a reverse diet - but that's for another blog post :) Depending on what your current health or weight loss goals are, will dictate how many calories you should be eating.
If your goal is weight loss: I would recommend starting a fat loss/dieting phase by subtracting 300-500 calories from your current maintenance
If your goal is to maintain your weight: I would recommend eating at your current maintenance or calculated maintenance
If your goal is to weight gain (even if that's in the form of building muscle): I would recommend starting in a slight surplus (eating above your maintenance calories) by adding 100-200 calories to your maintenance.
ANOTHER NOTE:
Another common scenario is women reaching out, wanting to get "tone". Achieving a toned body and a toned look requires 1 of 2 things to happen, or a combination of both. Achieving that lean and toned look requires you to either A) drop some body fat, so that the muscle you do have shows through by decreasing your overall body fat percentage or B) building muscle so that you have something to "show off".
If you already has a decent amount of muscle, but it's hiding behind some extra body fat, I'd recommend starting a fat loss phase so you can focus on lowering your body fat percentage. However, if you're someone who doesn't necessarily have a lot of muscle or is more "skinny fat", I would recommend not starting a fat loss phase, and instead, spend some time eating at or slightly above maintenance, so you can focus on building some lean muscle tissue first. It is possible for some women to gain muscle and shed body fat at the same time if they are in a fat loss phase; but that mostly applies to women who are new to weight lifting. However, if you're not new to exercise or you're an experienced lifter, it is much harder to achieve both of those goals simultaneously. More times than not, you need to focus on one goal or the other (losing fat or building muscle) because one requires you to be eating in a calorie deficit (losing weight/fat) and the other requires you to be eating at least your maintenance calories, so you are ensuring you're fueling your body with enough food to support muscle growth. If you need more personalized guidance on determining how many calories your body needs, as well as an appropriate macro split, I highly recommend checking out my personalized macro calculation. Hope this helps!