Calorie & BMR Calculator
Mifflin-St Jeor equation · By Stuart Mathieson · Updated October 2026
Feet
Inches
Results
Basal Metabolic Rate (BMR)
Calories burned at complete rest
Maintenance Calories (TDEE)
To maintain current weight
Daily Calorie Targets
Lose Weight
−500 cal/day
Maintain
Current weight
Gain Weight
+500 cal/day
Calculated using the Mifflin-St Jeor equation. These are estimates - individual needs vary. Consult a healthcare provider for personalized guidance.
How the calorie calculator works
The calculator first estimates your basal metabolic rate (BMR) - the calories your body uses at complete rest - with the Mifflin-St Jeor equation. It was published in 1990, based on measurements of 498 healthy adults:
It then multiplies your BMR by an activity factor to estimate your total daily energy expenditure (TDEE): the calories you burn on a typical day, including movement and exercise.
| Activity level | Typical week | Multiply BMR by |
|---|---|---|
| Sedentary | Little or no exercise | 1.2 |
| Lightly active | Exercise 1-3 days a week | 1.375 |
| Moderately active | Exercise 3-5 days a week | 1.55 |
| Very active | Exercise 6-7 days a week | 1.725 |
| Extra active | Athlete or physical job | 1.9 |
Worked example
A 35-year-old man who weighs 70 kg (154 lb), is 175 cm (5 ft 9 in) tall and is moderately active:
- BMR = 10 × 70 + 6.25 × 175 − 5 × 35 + 5 = 700 + 1,093.75 − 175 + 5 = 1,623.75, shown as 1,624 kcal a day.
- TDEE = 1,623.75 × 1.55 = 2,517 kcal a day.
- The targets shown are 2,017 kcal to lose weight and 3,017 kcal to gain weight.
For the same man, activity changes the daily total a lot: 1,949 kcal if sedentary, 2,233 lightly active, 2,517 moderately active, 2,801 very active and 3,085 extra active. A 35-year-old woman who weighs 62 kg and is 165 cm tall has a BMR of 1,315 kcal and a TDEE of 2,039 kcal at a moderate activity level.
Using your results
- The 500-calorie rule. The lose and gain targets are 500 calories below and above your TDEE. This comes from an old rule of thumb: a pound (about 0.45 kg) of body fat holds roughly 3,500 calories, so 500 a day is about a pound a week. In practice weight loss slows over time as your body adapts, so people usually lose less than this rule predicts. The NIH Body Weight Planner models that slowdown if you want a more detailed plan.
- It is an estimate. Equations like this predict the average for people of your size, age and sex; your own metabolism can be higher or lower. If your weight doesn't change the way you expect after a few weeks, adjust based on what actually happens.
- Activity is the biggest unknown. It is easy to overestimate how active you are. If you are unsure between two levels, choose the lower one.
- Not for everyone. The equation was developed for healthy adults. It isn't designed for children, pregnancy or breastfeeding, or medical conditions that affect metabolism - a doctor or registered dietitian can give personal advice.
Frequently asked questions
What's the difference between BMR and TDEE?
BMR is the energy your body needs at complete rest, just to keep basic functions running. TDEE adds your activity level on top, giving a realistic estimate of total daily calorie burn.
Why ±500 calories for losing or gaining weight?
One pound of body weight is roughly 3,500 calories, so a 500-calorie daily deficit or surplus works out to about a pound of change per week - a commonly used, moderate pace.
Which activity level should I choose?
Pick the one closest to your typical week, not just workout days - "Sedentary" fits little to no exercise, while higher levels assume regular structured exercise or a physically active job.
Which is more accurate, Mifflin-St Jeor or Harris-Benedict?
In the 1990 study that introduced it, the Mifflin-St Jeor equation predicted measured resting energy expenditure more closely, while the older Harris-Benedict equations overestimated it by about 5%. That is why Mifflin-St Jeor is widely used today.
Sources
- A new predictive equation for resting energy expenditure in healthy individuals - Mifflin MD, St Jeor ST et al., American Journal of Clinical Nutrition, 1990
- Body Weight Planner - National Institute of Diabetes and Digestive and Kidney Diseases (NIH)