Tip: The Mifflin-St Jeor Calorie Equation How many calories should you be eating? How many should you drop to lose fat? Here's how to know.


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May 13, 2016
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Need to lose some body fat? Here's how to get started:


Start with an equation to "ballpark" the number of calories you should be consuming daily. These equations aren't 100 percent accurate, but they're a good starting point.

The Mifflin-St Jeor equation to calculate resting metabolic rate (RMR) has been reported to be more accurate and is newer than some of the other ones out there. Here it is:

  • Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
  • Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) – 161
If you don't want to do the math, there are plenty of online calculators that'll do it for you.

Step 2: Factor in Your Activity​

Once you have your RMR you need to multiply your result by an activity factor to get a rough idea of how many calories you burn in a day. Here are the defined activity factors for the Mifflin-St Jeor equation:

RMRActivity FactorDefinition
x 1.2SedentaryLittle to no exercise
x 1.375Light ActivityLight exercise/sports 1-3 days per week
x 1.55Moderate ActivityModerate exercise/sports 3-5 days per week
x 1.725Very ActiveHard exercise/sports 6-7 days per week
x 1.9Extra ActiveVery hard exercise/sports and physical job

Step 3: Subtract Just the Right Number of Calories​

After you have an idea of your maintenance calories, calculating your calories for fat loss can be as simple as subtracting 250 for a theoretical half pound of fat loss per week, or subtracting 500 for a theoretical loss of one pound per week.
I say "theoretical" because this equation isn't exact. And as TC Luoma points out, calorie counts on food labels can also be BS. Still, it's a decent place to start.