How Many Calories A Day Do I Need To Lose Weight Fast

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If you've tried weight-loss methods that revolve around counting calories, like calories in-calories out (CICO) or a low-calorie diet, you know that how crucial creating a calorie deficit is to dropping pounds. It involves spending more calories than you consume. Sounds like simple math, right? Well, not exactly.

Sure, you can track your daily food intake using an app or a food journal, but making sure you have an accurate calorie count down for everything you eat can be tricky. And there is a lot more to consider besides logging your meals.

How Many Calories Should I Eat Per Day?

Every body and everyone is different in how many calories their body actually absorbs. Then, you need to consider the thermic effect of food (TEF), which is the number of calories your body uses just to digest food. You also want to know the number of calories you need to cover basic bodily functions, like breathing and pumping your heart (yep, your body naturally burns calories regularly!).

Plus, you need enough calories to cover any additional activities you are doing, whether it is chasing after your kids in the backyard, a walk around the city to run errands, or working out in the gym.

So, figuring out the right calorie deficit to shoot for takes a lot more than addition and subtraction. Here, health and wellness experts address all the questions you may have about how to calculate a calorie deficit.

How Many Calories Do I Need In A Day?

Roxana Ehsani, RD, is a nutritionist who specializes in sports dietetics. She is also a national media spokesperson for the Academy of Nutrition and Dietetics.

Some basics: A calorie is a measurement of energy. The calories in food supply your body with the fuel you need to survive. When you eat food, it’s broken down by your body to release energy to be used right away or stored for later, depending on what you need at that moment.

Your body needs to take in a certain number of calories to maintain your weight, says Keri Gans, RD, the author of

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And so, “a calorie deficit is when you consume fewer calories than your body requires to stay at its current weight, ” she explains. If you take in fewer calories than your body needs, your body will turn to the calories you have stored up to burn for energy. As a result, you’ll lose weight.

Every person’s caloric needs and deficits are different and depend on a bunch of factors, like how much you exercise, your genes, your hormones, and your metabolism, notes Sonya Angelone, RD, a spokeswoman for the Academy of Nutrition and Dietetics.

And it can be challenging to create a calorie deficit in a healthy way. For example, most people might not pick the correct total amount of calories to go off, then create too much of a restrictive calorie deficit for themselves to follow, says Roxana Ehsani, RD, LDN, a national media spokesperson for the Academy of Nutrition and Dietetics.

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A woman may need 2, 400 calories a day based on her height, weight, and training volume (a very active athlete), but thinks she only needs 1, 800 calories per day to maintain her weight. But if she decides she wants to lose weight, she may create an even bigger calorie deficit and cut out 500 more calories, ending up with 1, 300-calorie meal plan.

It can be a little complicated to figure out your exact calorie deficit, but, in general, it’s thought that shaving 500 calories from your daily intake should lead to one pound of weight loss per week.

“The classic definition is based on the fact that one pound of fat contains 3, 500 calories, ” Angelone says. “If you eat 500 calories less than the amount you need to maintain your weight, you will lose one pound in a week.” If you want to lose two pounds a week, you might try a 1, 000-calorie daily deficit. You just typically don’t want to cut any more calories than that. “Healthy weight loss is considered one to two pounds per week, ” Gans notes.

How Many Calories Should I Burn A Day To Lose Weight?

You don’t necessarily have to drop 500 calories a day from your diet to lose weight, though. “Any deficit will lead to weight loss, ” Angelone says. “It will just take more or less time, depending how great the deficit.”

If you're burning more calories through exercise than you consume in a day, you will have a calorie deficit, says Dana Ellis Hunnes, PhD, a senior dietitian at UCLA Medical Center. This is why any extra movement, like daily exercise, walks, and workouts can help.

But you don't want to just ramp up your physical activity and completely neglect your diet. “It is so easy to out-eat anything you burn, ” says Hunnes. “Cutting out calories is probably more effective than trying to burn off what you eat.” However, she believes doing both is important and more effective.

Diets And Calories: How Many Calories Do I Need To Maintain My Weight?

Of calories you take in, Angelone notes. (Some nutrients, like sugar, are used up more easily and quickly than fiber, she explains.) Your body also compensates for short-term calorie changes, temporarily raising your metabolism if you eat more for a few days, and lowering it if you eat less.

Your activity levels, age, height, quality of sleep, and weight all affect the exact number of calories you need. Here's a handy graphic for you to find your number based on how old and active you are.

That said, at the very minimum, women need 1, 200 calories per day to function properly. This is known as the basal metabolic rate, which is the minimum number of calories your body needs to function properly every day.

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If you go below that number, you may need even fewer calories at some point to maintain your weight, which becomes increasingly difficult and not sustainable. Also, you will tend to store the calories you eat if and when you go below your basal metabolic rate, says Hunnes.

There are a lot of different ways to figure out an appropriate calorie deficit, and some are more accurate than others. There are different ways of calculating calorie needs, but Angelone says she usually uses the Harris-Benedict Equation, Mifflin-St Jeor Equation, or Katch-McArdle Formula with her clients. Here’s how to figure out your deficit in a few different ways.

Every practitioner has a slightly different approach. Angelone will take calculations based on body measurements like weight and height, along with exercise level. And Gans prefers a more low-key approach. “I try to leave math out of the equation and instead focus with my patient on making small changes that can naturally lead to weight loss, ” she says.

How To Figure Out How Many Calories To Have Per Day

But some practitioners may even send you for metabolic testing, which measures how many calories you burn at rest (like when you’re sitting around), to try to get an accurate number.

Found that the Mifflin-St. Jeor equation is very accurate. This equation calculates your basal metabolic rate (BMR), which is the minimum number of calories your body burns at rest.

For women, the Mifflin-St. Jeor equation is: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161.

How Many Calories Should You Consume In A Day?

So, the BMR equation for, a 25-year-old woman who is 5'4 and weighs 150 pounds would be this: BMR= (10 x 68) + (6.25 x163) - (5 x 25) -161 = 1, 413 calories

The Harris Benedict equation is often used for comparison. That equation is: BMR = 655.1 + (9.563 x weight in kg ) + (1.850 x height in cm) - ( 4.676 x age in years).

For the same 150-pound woman, the BMR using the Harris Benedict equation would be: BMR= 655.1 + (9.563 x 68) + (1.850 x 163) - ( 4.676 x 25) = 1, 490 calories

How Many Calories Do I Need In A Day To Maintain, Gain & Lose Weight

The results are slightly different depending on which formula you use. And Angelone stresses, “This is still an estimate, since so many factors affect weight loss.”

Don’t feel like doing the math? There are plenty of online calculators that can help. The National Institute of Health’s Body Weight Planner is a good one to try, Angelone says. It looks at your current weight and fitness level, along with your weight-loss goals, and helps map out how many calories you need to take in to lose the weight over the period of time you specify. A nice perk: It also tells you how many calories to aim for once you reach your goal weight to help maintain it.

There are a few different ways you can go about creating a calorie deficit and, ideally, you’d factor in a combo of all of these changes.

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Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.

Ashley Martens is a Wellness Writer based in Chicago, Illinois. With a digital marketing background and her knowledge of general nutrition and