What is the difference between BMR and TDEE?

BMR is the calories burned at complete rest. Total daily energy expenditure (TDEE) is BMR multiplied by an activity factor to include movement and exercise, so TDEE is always larger than BMR.

Which equation should I use, Mifflin-St Jeor or Harris-Benedict?

Mifflin-St Jeor is generally preferred today because validation studies found it more accurate for the modern population. Harris-Benedict tends to estimate slightly higher and is offered here for comparison.

Does BMR change over time?

Yes. BMR tends to fall with age and with loss of lean muscle, and it rises with greater body mass. Building or preserving muscle is one of the few ways to keep resting metabolism higher.

Should I eat only my BMR in calories?

No. Eating at your BMR ignores all the energy you spend moving, working, and exercising. Use your TDEE, not BMR, as the baseline for weight maintenance, and consult a professional before aggressive deficits.

BMR Calculator

Gender

Age30 years

Height

Weight

lbs

Formula

Basal Metabolic Rate1,783 cal/day

Basal metabolic rate (BMR) is the number of calories your body burns at complete rest just to keep vital functions running — breathing, circulation, and cell maintenance. This calculator estimates BMR from your sex, age, height, and weight using either the modern Mifflin-St Jeor equation or the older Harris-Benedict equation. BMR is the foundation for working out total daily calorie needs once activity is added on top.

Formula

Mifflin-St Jeor: BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + s (s = +5 male, −161 female)

weight: Body weight in kilograms (pounds × 0.453592)
height: Height in centimetres (inches × 2.54)
age: Age in years
s: Sex constant: +5 for men, −161 for women (Mifflin-St Jeor)

How it works

Enter your sex, age in years, height in inches, and weight in pounds; the tool converts to centimetres and kilograms (× 2.54 and × 0.453592) before calculating.
Choose the equation: Mifflin-St Jeor (today's default, generally most accurate) or Harris-Benedict (the classic 1919/1984 revision).
The result is your resting calorie burn per day, rounded to a whole number, which you can multiply by an activity factor to estimate total daily energy expenditure.

Worked examples

A 30-year-old man, 5 ft 10 in (70 in) and 180 lb, using Mifflin-St Jeor.

Convert: 70 × 2.54 = 177.8 cm; 180 × 0.453592 = 81.65 kg.
BMR = 10·81.65 + 6.25·177.8 − 5·30 + 5 = 816.5 + 1111.25 − 150 + 5.
Sum = 1782.7 calories per day.

BMR ≈ 1,783 cal/day at rest.

The same man using the Harris-Benedict equation.

Harris-Benedict (male): 88.362 + 13.397·81.65 + 4.799·177.8 − 5.677·30.
= 88.362 + 1093.86 + 853.26 − 170.31.
Sum ≈ 1865.1.

BMR ≈ 1,865 cal/day, slightly higher than Mifflin-St Jeor.

Frequently asked questions

What is the difference between BMR and TDEE?: BMR is the calories burned at complete rest. Total daily energy expenditure (TDEE) is BMR multiplied by an activity factor to include movement and exercise, so TDEE is always larger than BMR.
Which equation should I use, Mifflin-St Jeor or Harris-Benedict?: Mifflin-St Jeor is generally preferred today because validation studies found it more accurate for the modern population. Harris-Benedict tends to estimate slightly higher and is offered here for comparison.
Does BMR change over time?: Yes. BMR tends to fall with age and with loss of lean muscle, and it rises with greater body mass. Building or preserving muscle is one of the few ways to keep resting metabolism higher.
Should I eat only my BMR in calories?: No. Eating at your BMR ignores all the energy you spend moving, working, and exercising. Use your TDEE, not BMR, as the baseline for weight maintenance, and consult a professional before aggressive deficits.

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