Mifflin St. Jeor Calculator

Below is the Mifflin St. Jeor Calculator.

This is the formula that I use to calculate my PT clients’ calories, I’m so excited to have a calculator version now!

Enter your details below and it will estimate your BMR, which is the amount of energy you use each day at rest. Because it’s ‘at rest’ we need to use the ‘Activity Multiplier to include everything you do (work, walking, stairs, exercise etc).

Once we have that final number we can amend it to match your goals.

Directions for using the calculator:

Select your sex.
Enter in your weight in kgs.
Enter in your height in cm.
Enter in your age. You now have your BMR.
Next you will want to multiply your BMR by activity multiplier.

Use the chart below to estimate the amount to multiply it by.

When you have your final number you can amend it to match your goals.


I like to take -300 off my calories for fat-loss.

You could take up to -500 calories off but for me -300 works well as a steady loss whilst being able to enjoy the lifestyle and food I love.

Maintenance - Increase Strength & Look More Lean

You can keep your calories the same and increase your weight training. 

This will change your body composition. Overtime you will increase your muscle and decrease your fat.

Your weight will stay the same but you will look more toned, lean and athletic.

BMR Calculator