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BMR Calculator (Basal Metabolic Rate)

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to keep you alive and maintain vital functions like breathing, circulation, and cell production.

Sex influences baseline muscle mass and metabolic rate calculations.

Mifflin–St Jeor is recommended for general use. Katch–McArdle requires known body fat percentage.

Required only when using the Katch–McArdle formula.

Calculated Result
1,659 kcal/day

Basal metabolic rate (BMR)

Per day

1,659 kcal/day

Per minute

1.15 kcal/min

In kilojoules

6,940 kJ/day

Per kilogram of body mass

23.7 kcal/kg/day

Comparison band

Typical (23.7 kcal/kg/day)

Harris–Benedict, revised 1984

1,707 kcal/day

Typical basal metabolic rate — Basal metabolic rate varies a great deal between people of the same weight and height because of genetics, muscle mass, thyroid function and body temperature. Read this as a population-level estimate, not a measurement, and treat it as a screening figure rather than a clinical one.

Calculation Breakdown

  1. Normalise the inputs to metric70 kg and 175 cm are already metric.kg, cm
  2. Substitute into Mifflin–St Jeor(10 × 70) + (6.25 × 175) − (5 × 28) + 5BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5 (male) or − 161 (female)
  3. Evaluate700 + 1,093.8 − 140 + 5 = 1,658.75 kcal/dayBMR
  4. Convert to kilojoules1,659 kcal × 4.184 = 6,940.2 kJ per daykJ = kcal × 4.184

Energy Expenditure Breakdown

Interactive visualization based on your current inputs

Energy
0.04158301.2k1.7kPer DayPer 12 HoursPer HourPeriodCalories (kcal)

What Is the BMR Calculator (Basal Metabolic Rate)?

Basal Metabolic Rate is the baseline quantity of daily energy expended while physically and psychologically at rest.

It represents the absolute minimum caloric fuel needed to support internal organ homeostasis.

How Does the BMR Calculator (Basal Metabolic Rate) Work?

Weight, height, and age are adjusted by sex-specific constants to model metabolic body surface area.

The result provides a daily caloric baseline alongside per-minute and kilojoule conversions.

BMR Calculator (Basal Metabolic Rate) Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

BMR=10W+6.25H−5A+s,s={+5male−161female\text{BMR} = 10W + 6.25H - 5A + s, \quad s = \begin{cases} +5 & \text{male} \\ -161 & \text{female} \end{cases}

Variable Definitions

SymbolVariable Meaning & Units
WWeight in kilograms
HHeight in centimetres
AAge in years
sSex adjustment factor

The Mifflin–St Jeor equation estimates calories required per day to sustain vegetative biological function at thermo-neutral rest.

How to Use the BMR Calculator (Basal Metabolic Rate)

  1. Select your unit preference (metric or imperial).
  2. Provide your biological sex, age, current weight, and height.
  3. Choose the predictive formula of your choice.
  4. Review your resting calorie burn per day.

Step-by-Step Example Calculation

A 28-year-old male weighing 70 kg and 175 cm tall

Input Values:

system:metric
sex:male
age:28
weight:70
height:175
formula:mifflin
Worked Steps: (10 × 70) + (6.25 × 175) - (5 × 28) + 5 = 1,659 kcal/day at rest.

Understanding Your Result

Your daily BMR is your non-negotiable metabolic burn.

Multiply this number by an activity factor to determine your Total Daily Energy Expenditure (TDEE).

Factors That Affect the Result

  • Lean muscle mass: more muscle mass elevates baseline caloric requirements.
  • Thyroid hormone levels: thyroid hormones directly regulate cellular metabolic rate.
  • Genetics and age: metabolic activity naturally declines with advancing age.

When Should You Use This Calculator?

  • Establishing foundational calorie targets for body recomposition.
  • Determining minimum safe nutritional intake levels.

Assumptions & Limitations

  • Standard predictive formulas estimate population averages and may vary by ±10-15% from indirect calorimetry.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Implements official published equations from peer-reviewed clinical nutrition literature.

Standard Reference: Mifflin, M. D., et al. (1990). "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr, 51(2), 241-249.

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