Do You Know Your Personal Calorie Count?
As a nutritionist, one of the most frequent questions my clients come to me with is.
“How many calorie should i eat in a day?”
I usually whip out my calculator and plug some numbers into an equation (starting with the Mifflin-St Jeor equation, if you must know!) and come up with a pretty accurate estimate.
The good news…
… I’m here to share those very same calculations with YOU, so you will be able to determine your own calorie count.
So rev up your calculator and let’s get calorie counting!
First, decide whether you want to:
- Lose weight
- Maintain weight
- Gain weight
Regardless of your choice, if you want to figure out how many calories to eat in a day, you first have to determine how many calories you burn in a day. The number of calories you burn in a day is referred to as your “total daily energy expenditure (TDEE).”
Calorie count: Determining your TDEE
Your total daily energy expenditure (TDEE) is the calorie count your body requires to allow you to partake in all the activities you do in a 24 hour period (including breathing and thinking). Let’s just call this your “maintenance calorie level” in order to keep the discussion easy to follow.
If your goal is to maintain weight, once you have calculated your maintenance calorie level, you can put the calculator away. If you want to lose weight, you will have to subtract some calories from this number, and if you want to gain weight, you will have to add some calories.
I know, you’re itching to get to the math…
…so here we go!
Calculating your maintenance calorie level is a 2 step process:
- Determine your metabolism
- Multiply metabolism by an activity factor
1. Calorie count: Determining Your Metabolism
You can use the metabolism calculator on this site OR calculate for yourself.
(I recommend at least trying to calculate your own calorie count. You’ll end up with a better understanding! If you end up too confused, you could always enlist the help of a nutrition professional. Me!)
To calculate for yourself, use one of the following equations (depending on gender and measurement system):
(10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5Male/metric: metabolism =
Female/metric: metabolism =
(10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161
Male/English: metabolism =
(4.545 x weight in lbs) + (15.875 x height in inches) – (5 x age in years) + 5
Female/English: metabolism =
(4.545 x weight in lbs) + (15.875 x height in inches) – (5 x age in years) – 161
50 year old female, 5’6″, 155 pounds:
metabolism = 704.5 + 1047.8 – 250 – 161 = 1341
This equation does not take into consideration lean body mass. Therefore, the results will be skewed if you are extremely muscular (will underestimate calorie needs) or obese (will overestimate calorie needs).
If you’ve had your body composition tested and know your lean body mass, then you can get the most accurate estimate of your metabolism with the following equation:
Metabolism/Metric = 370 + (21.6 x lean mass in kg) or
Metabolism/English = 370 + (9.82 x lean mass in lbs)
Note: The same formula is used for both men and women.
2. Calorie count: Multiplying by your activity factor
Once you know your metabolism, you can calculate TDEE, or maintenance calorie level, by multiplying your metabolism by an activity factor from the chart below:
- Sedentary = metabolism X 1.2 (little or no exercise, desk job)
- Lightly active = metabolism X 1.375 (light exercise 1-3 days/wk)
- Moderately active = metabolism X 1.55 (moderate exercise 3-5 days/wk)
- Very active = metabolism X 1.725 (hard exercise 6-7 days/wk)
- Extremely active = metabolism X 1.9 (hard daily exercise or physical job or 2X/day training)
The result you get will be your maintenance calorie level:
metabolism x activity factor = “maintenance calorie level”
Using our 50 year old female above, assuming she is moderately active:-metabolism of 1341 x activity factor 1.55 = 2079 calories.
This means she can eat nearly 2100 calories per day and maintain her weight.
What if she (or YOU) want to lose weight?
Well, we just have to do a tiny bit more math.
Calories not only count, they are the bottom line when it comes to your bottom line. In order to lose one pound of body fat, you have to create a deficit of 3500 calories over some course of time.
In order to lose 1 pound of body fat in one week, you would need to create a calorie count deficit of 500 calories per day x 7 days per week:
500 calories x 7 days = 3500 calories = 1 pound of body fat
The reverse is true too. If you want to gain 1 pound in one week, you need to add 500 calories per day to your maintenance calorie level.
Want to lose 2 pounds per week? Well, you’d have to subtract 1000 calories from your maintenance calorie level every day.
NOTE: However, eating too little can actually work against you.
So in the case of our 50 year old, 5’6″, 155 pound female:
- Her metabolism is 1342 calories.
- She requires ~2100 calories per day to maintain her weight.
- She should eat ~1600 calories per day to lose 1 pound of body fat per week.
- If she tried to lose 2 pounds per week by eating only 1100 calories per week, this would put her at an unhealthy calorie level and could actually cause her metabolism to slow. (Not to mention that she’d probably have trouble sticking to this diet for very long anyway!)
- If she started eating 2600 calories per day, she would gain 1 pound per week.