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.

Need to lose some body fat? Here’s how to get started:

Step 1: Calculate Your RMR

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:

RMR Activity Factor Definition
x 1.2 Sedentary Little to no exercise
x 1.375 Light Activity Light exercise/sports 1-3 days per week
x 1.55 Moderate Activity Moderate exercise/sports 3-5 days per week
x 1.725 Very Active Hard exercise/sports 6-7 days per week
x 1.9 Extra Active Very 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.