How Many Calories Do I Need in a Day?

Knowing how many calories to consume per day is not as simple as it sounds.

The first step in making any body composition change, even before asking, "How many calories do I need?" is to decide your goal and the caloric state into which you want to put your body. If your goal is weight loss, you need to be in a caloric deficit, or consuming fewer calories than you expend. To gain weight, you will need to be in a caloric surplus, or consuming more calories than you expend. And to maintain, you will need a balance between calories consumed and expended.

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Although protein, carbohydrate and fat ratios are important, the single most important factor in weight change is calorie intake. The old mantra remains true: calories in versus calories out. So, once you have established your body composition goal, it's time to answer the question, "How many calories do I need to reach that goal?"

Before we dive in on how to answer this question, the best piece of advice I can give on determining how many calories you need is "don't stress yourself out over it." None of the calculations below will ever be 100-percent precise. Everyone is different, and several factors influence people's metabolic rate. Hormones, muscle-to-fat ratio, age, and genetics all play a role in metabolic rate and daily calorie needs. A good example is your friend who eats everything in sight and never gains a pound.

The differences among individual metabolic rates makes it difficult to calculate calories with any one formula or equation. The formulas provided below work for a large percentage of people, but the most accurate way to find how many calories you need in a day is to precisely track your food intake for a week or two. If you are satisfied with a "ballpark" number, there is no need to do this. But if you want the most accurate number, follow the steps below.

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  1. Record your starting body weight.
  2. Track everything you eat or drink for the allotted time frame.
  3. At the end of your tracking period, divide your total calories by the number of days you tracked. (If you ate a total of 21,000 calories in a week, that's 21,000/7 days for an average of 3,000 calories per day.)
  4. Record your weight after the tracking period.

If your weight remained the same, 3,000 calories/day is close to your maintenance calorie level.

If you gained weight, your daily calorie needs are less than 3,000 per day. How much less depends on the amount of weight you gained. If your weight increased by .25 pounds, you might do better with 2,750/day. If you gained over one pound in a week, you may need to drop closer to 2,250.

The same scenario applies to losing weight, only in reverse.

Many formulas require lots of inputs (like age and height) and include conversions with more math. If you just need a place to start, a fairly simple method you can use is a bodyweight multiplier, which takes into account your current body weight and the amount of time you exercise or train each week. The only variable that changes with a bodyweight multiplier is the base number that correlates with your goal.

Weight Loss

  • Body weight X (9 + Weekly Training Hours)
  • Example: A 150-poung woman exercising 3 hours per week: 150 X (9+3) = 1800 calories/day

Weight and Muscle Gain

  • Body weight X (14 + Weekly Training Hours)

Weight Maintenance

  • Body weight X (11-12 + Weekly Training Hours)

There are a few other factors to consider with bodyweight multipliers.

  • Lifestyle and work environment – If you have a completely sedentary job and lifestyle (like a student), your numbers may be a bit lower. On the other hand, if you move around all day or perform manual labor, you'll likely need to increase these calories.
  • Your metabolic rate is not set in stone — As you gain or lose weight, your metabolic rate may change. A heavier person typically burns more calories at rest than a lighter person.
  • Training intensity – If you are a competitive athlete, you may need to add training hours to account for the elevated intensity. If you are only walking the dog a few times a week, you may want to be less generous with your training hour total.

Remember, these numbers are only a place to start and will likely need to be adjusted over time. Avoid making too drastic of a change all at once. Decreasing or increasing your calories by over 500 at a time is a mistake and is not a sustainable strategy. The best rate of weight loss or gain is around one pound per week, with a maximum of around two pounds per week in either direction. Sticking to a pace that is sustainable will benefit your overall health and set you up for long-term success.

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