Introduction
This Mifflin-St Jeor calculator helps you find out how many calories your body burns each day. It figures out two key numbers: your BMR (Basal Metabolic Rate) and your TDEE (Total Daily Energy Expenditure). Your BMR is the number of calories your body needs just to stay alive at rest — things like breathing, pumping blood, and keeping your brain working. Your TDEE takes your BMR and adds in the calories you burn through daily movement and exercise.
The Mifflin-St Jeor equation is one of the most accurate formulas for estimating calorie needs. It uses your age, height, weight, and biological sex to calculate your BMR. Studies show it comes within 10% of most people's true metabolic rate, which makes it a trusted tool used by doctors and dietitians.
Knowing your TDEE is useful whether you want to lose weight, gain muscle, or maintain your current size. To lose weight, you eat fewer calories than your TDEE. To gain weight, you eat more. To stay the same, you match it. Enter your details below, pick your activity level, and the calculator will do the rest — including a full step-by-step breakdown of the math.
How to Use Our Mifflin-St Jeor Calculator
Enter a few details about your body and activity level below. The calculator will show your BMR (calories burned at rest) and your TDEE (total calories burned per day).
Pick your unit system: Click "Imperial (US)" to use pounds and feet, or click "Metric" to use kilograms and centimeters.
Enter your age: Type your age in years. You must be between 15 and 80 years old to use this calculator.
Select your biological sex: Choose either Male or Female. The formula uses a different number for each sex to estimate your metabolism.
Enter your height: In Imperial mode, type your height in feet and inches. In Metric mode, type your height in centimeters. If you're curious about how your height compares to others, you can check our Height Calculator.
Enter your weight: In Imperial mode, type your weight in pounds or switch to stones. In Metric mode, type your weight in kilograms.
Choose your activity level: Pick the option from the dropdown that best matches how much you exercise in a normal week. Options range from Sedentary (little or no exercise) to Extra Active (very intense daily exercise or a physical job).
Click "Calculate BMR & TDEE": Your results will appear below. You will see your BMR, your TDEE, a step-by-step breakdown of the math, a comparison table for all activity levels, a bar chart, and your BMI.
What Is the Mifflin-St Jeor Calculator?
This calculator uses the Mifflin-St Jeor equation to find out how many calories your body burns each day. It gives you two key numbers: your BMR and your TDEE.
What Is BMR?
BMR stands for Basal Metabolic Rate. It is the number of calories your body needs just to stay alive while doing nothing at all. Even when you sleep, your body uses energy to breathe, pump blood, and keep your organs working. Your BMR is that baseline energy cost. It does not include walking, eating, or any kind of movement. For a broader look at resting metabolism using multiple equations, try our dedicated BMR Calculator. A closely related measure is your Resting Metabolic Rate, which you can estimate with our RMR Calculator.
What Is TDEE?
TDEE stands for Total Daily Energy Expenditure. It is the total number of calories you burn in a full day, including all your activity. Your TDEE takes your BMR and multiplies it by an activity factor based on how much you move and exercise during a typical week. If you want to maintain your current weight, you should eat roughly the same number of calories as your TDEE. You can also explore our standalone TDEE Calculator for additional activity breakdowns.
How the Mifflin-St Jeor Equation Works
The Mifflin-St Jeor equation was created by doctors M.D. Mifflin and S.T. St Jeor in 1990. It uses four inputs to estimate your BMR:
- Weight in kilograms
- Height in centimeters
- Age in years
- Biological sex (male or female)
The formulas are:
- Men: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5
- Women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161
Most nutrition experts consider this equation the most accurate BMR formula for the general population. It replaced the older Harris-Benedict equation, which tends to overestimate calorie needs. For a general overview of your daily calorie needs across different goals, you can also use our Calorie Calculator.
Why Your Activity Level Matters
Your BMR only covers rest. To get your true daily calorie needs, the calculator multiplies your BMR by an activity multiplier. Someone with a desk job who does not exercise will have a much lower TDEE than someone who trains hard six days a week. Picking the right activity level gives you a more useful and accurate result. If you want to see how many calories specific activities burn, try our Calories Burned Calculator or our Walking Calorie Calculator for everyday movement.
What You Can Do With Your Results
Once you know your TDEE, you can use it to guide your eating habits:
- Maintain weight: Eat roughly the same calories as your TDEE.
- Lose weight: Eat fewer calories than your TDEE. A common target is 500 calories below your TDEE per day, which works out to about one pound of fat loss per week. Our Calorie Deficit Calculator and Weight Loss Calculator can help you plan a safe deficit.
- Gain weight: Eat more calories than your TDEE. Our Weight Gain Calculator can help you set a calorie surplus target.
After setting your calorie target, break it into specific nutrients with our Macro Calculator or dial in your daily Protein Calculator to support muscle growth. You may also find it helpful to track your body fat percentage, check your ideal body weight, or ensure you're drinking enough water with our Water Intake Calculator.
These numbers are estimates. Things like genetics, muscle mass, hormones, and health conditions can all affect how many calories you truly burn. If you have specific health goals, talk to a doctor or registered dietitian for advice tailored to you.