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Health & Fitness

BMR vs TDEE: What's the Difference?

Understand the difference between BMR (calories burned at rest) and TDEE (total daily calories burned), how activity multipliers work, and why both are estimates.

Understanding the Calculation

BMR represents the energy your body needs for basic functions — breathing, circulation, cell repair — if you did nothing but lie still for 24 hours. It does not include any calories burned from walking, working, exercising, or even digesting food.

TDEE builds on BMR by adding an activity multiplier that accounts for how much you actually move in a typical day. Because almost nobody is completely sedentary in the literal sense, TDEE is almost always the more useful number for everyday calorie planning.

Both numbers are estimates, not lab measurements. Formula-based BMR estimates (like Mifflin-St Jeor, used below) are considered accurate to within roughly a 10% margin for most people, and the activity multiplier used to convert BMR into TDEE adds further uncertainty on top of that.

The Formula

Mifflin-St Jeor BMR Formula and TDEE Multiplier
Men: BMR = 10*weight(kg) + 6.25*height(cm) - 5*age + 5 | Women: BMR = 10*weight(kg) + 6.25*height(cm) - 5*age - 161 | TDEE = BMR * Activity Multiplier

The Mifflin-St Jeor equation is a widely used formula for estimating BMR from weight, height, age, and sex. Multiplying BMR by an activity factor scales it up to estimate total daily calories burned, including movement and exercise.

Variables & Definitions

weight(kg)— Body Weight
Body weight in kilograms.
height(cm)— Height
Height in centimeters.
age— Age
Age in years.
Activity Multiplier— Activity Level Factor
A multiplier from roughly 1.2 (sedentary) to 1.9 (very heavy activity) reflecting typical weekly activity level.

Worked Example

Worked Example: BMR and TDEE for a Moderately Active Adult

A 30-year-old male, 80 kg, 180 cm tall, who exercises moderately 3-5 days per week.

Starting Inputs
  • Sex:Male
  • Age:30
  • Weight:80 kg
  • Height:180 cm
  • Activity Level:Moderately active (multiplier 1.55)
Step-by-Step Calculation
  1. 1

    Calculate BMR using the Mifflin-St Jeor formula (men)

    Plug weight, height, and age into the men's version of the formula.

    BMR = 10*80 + 6.25*180 - 5*30 + 5 = 800 + 1125 - 150 + 5
    Result: BMR = 1,780 kcal/day
  2. 2

    Apply the activity multiplier for moderately active

    Multiply BMR by 1.55, the standard multiplier for exercising at moderate intensity 3-5 days per week.

    TDEE = 1780 * 1.55
    Result: TDEE ≈ 2,759 kcal/day
  3. 3

    Compare a different activity level

    If the same person were sedentary instead (multiplier 1.2), TDEE would be lower: 1780 * 1.2 = 2,136 kcal/day — a difference of over 600 calories from activity level alone.

    1780 * 1.2 = 2,136
    Result: TDEE ≈ 2,136 kcal/day (sedentary)
Conclusion: The same BMR (1,780 kcal/day) produces very different TDEE estimates depending on activity level — which is why picking an honest activity multiplier matters more than the BMR formula chosen.

Calculate Your Own Numbers

Put these formulas into practice with our free, in-browser calculators:

BMR Calculator

Estimate basal metabolic rate using the Mifflin-St Jeor formula.

Open calculator

TDEE Calculator

Estimate total daily energy expenditure by combining BMR with an activity multiplier.

Open calculator

Calorie Calculator

Estimate daily calorie targets for maintaining, losing, or gaining weight.

Open calculator

What the Results Mean For You

  • Common activity multipliers: sedentary (little or no exercise) ≈1.2, lightly active (light exercise 1-3 days/week) ≈1.375, moderately active (moderate exercise 3-5 days/week) ≈1.55, very active (hard exercise 6-7 days/week) ≈1.725, extremely active (very hard exercise or physical job) ≈1.9.
  • People tend to overestimate their own activity level, which overestimates TDEE. When in doubt, it's usually more accurate to pick the lower of two activity levels that seem close.
  • Both BMR and TDEE are starting estimates, not fixed numbers. Actual calorie needs vary with genetics, muscle mass, hormones, and day-to-day activity — tracking real-world weight change over a few weeks is the most reliable way to calibrate the estimate for a specific person.

Common Pitfalls & Mistakes

Using BMR as a daily calorie target

BMR only accounts for calories burned at complete rest. Eating at exactly BMR level ignores all calories burned through daily activity and will usually create a larger calorie deficit than intended.

Picking an activity multiplier that doesn't match real behavior

Choosing 'very active' while actually exercising once or twice a week inflates TDEE and can lead to eating more than the body actually needs for the stated goal.

Treating the result as an exact number rather than an estimate

Formula-based BMR and TDEE are estimates with a real margin of error — they're a starting point to adjust from based on actual results over time, not a precise medical measurement.

Authoritative References & Sources

All formula representations and regulatory context are verified against authoritative public sources:

  • A New Predictive Equation for Resting Energy Expenditure in Healthy IndividualsAmerican Journal of Clinical Nutrition (Mifflin, St Jeor, et al., 1990)

    The original published study establishing the Mifflin-St Jeor BMR equation.

    Visit source documentation