Health & Fitness
BMR Calculator
Estimate daily, weekly, hourly, and body-weight-normalized basal energy using the Mifflin-St Jeor equation. The page shows how weight, height, age, and the selected equation constant enter the calculation, then places BMR inside a 24-hour resting-energy clock with practical interpretation, limitations, and FAQ.
Estimated basal metabolic rate-
Estimated basal weekly energy-
BMR per kg body weight-
Average basal energy per hour-
Decision view
Twenty-four-hour basal energy clock
Twenty-four-hour basal energy clockThe daily equation estimate is distributed around a 24-hour resting-energy clock while weekly and body-weight-normalized references remain separate.
Exact scenario comparisonBody weight (kg) changes while all other entered assumptions remain constant.
| Body weight (kg) | Estimated basal metabolic rate | Estimated basal weekly energy | BMR per kg body weight | Average basal energy per hour |
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How to use BMR Calculator
- Enter a recent body weight, standing height, age, and the equation constant corresponding to the Mifflin-St Jeor form being used.
- Treat the result as an estimated resting baseline before activity, digestion, growth, pregnancy, recovery, and goal adjustments.
- For daily-energy planning, combine BMR with an appropriate activity model and compare predictions with observed weight and intake trends.
Calculator guide
Understanding BMR Calculator
Basal metabolic rate estimates the energy a resting body uses to maintain essential functions such as circulation, breathing, temperature regulation, and cellular activity. It is a baseline—not a daily calorie target and not a direct measurement of metabolism.
Calculation method
How the calculation works
Apply the Mifflin-St Jeor form using weight, height, age, and the selected sex constant to estimate basal energy expenditure. Use BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age in years + the selected equation constant. Multiply by seven for weekly basal energy, divide by 24 for an hourly average, and divide by body weight for the displayed kcal/kg reference.
Energy model
What sits above the basal layer
Total daily energy expenditure contains several components that the BMR result does not claim to measure.
A calorie target based only on BMR would usually omit meaningful parts of daily energy use.
Worked situations
Practical examples
- At 72 kg, 175 cm, age 35, and a constant of 5, the equation estimates about 1,649 kcal/day.
- The same result averages roughly 68.7 kcal per hour, although real energy expenditure is not perfectly uniform through the day.
- A weekly basal estimate near 11,543 kcal still excludes exercise, normal movement, and digestion.
Better inputs
Useful tips
- Use the same measurement conditions when comparing changes over time; hydration and scale variation can affect body weight.
- Do not add exercise calories to BMR directly without also representing ordinary daily movement and food-related energy expenditure.
- When an accurate resting value matters, consider indirect calorimetry performed under controlled clinical or laboratory conditions.
Before relying on the result
Limitations and common mistakes
- Mifflin-St Jeor is a population equation and can differ from measured resting expenditure for an individual.
- Body composition, illness, medication, endocrine status, temperature, pregnancy, growth, dieting history, and measurement error are not explicitly modeled.
- The sex constant is an equation parameter and does not capture the full biological and clinical variation relevant to metabolic assessment.
Reference
Key terms
- Basal metabolic rate
- Estimated energy required for essential body functions under standardized resting conditions.
- Resting energy expenditure
- A closely related measured or estimated resting value, often obtained under less restrictive conditions than true basal testing.
- Thermic effect of food
- Energy used to digest, absorb, and process food; it is not included in BMR.
- Activity expenditure
- Energy used for exercise and non-exercise movement beyond the resting baseline.
Important note
Calculated from the entered measurements using the displayed method. It is a general reference and does not replace diagnosis or individualized professional guidance.
Frequently asked questions
Is BMR the number of calories I should eat?
No. BMR is a resting baseline. Daily intake planning generally considers activity, food processing, goals, health, and observed response.
Why can a smartwatch show a different number?
Devices often estimate total or active calories using different equations and sensor data, so they are not reporting the same quantity.
Does losing weight reduce estimated BMR?
Lower entered body weight usually lowers the equation result, but individual adaptation and body-composition changes are not captured fully.
Is the hourly value a literal hourly burn?
No. It is the daily estimate divided by 24 for scale; actual expenditure varies across sleep, waking, temperature, and physiology.