Basal Metabolic Rate (BMR) Calculator
Estimate your resting calorie burn, compare BMR formulas, and calculate a quick TDEE using activity multipliers.
Your details & options
Formulas
Results are estimates. For medical advice, consult a clinician.
Results
Example BMR calculation
Example: male, age 30, height 180 cm, weight 80 kg.
Mifflin–St Jeor BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 1,780 kcal/day.
If moderately active, estimated TDEE = 1,780 × 1.55 = 2,759 kcal/day.
About this BMR calculator
Release update v1.1
- Added a primary formula for TDEE selector so daily calorie estimates use a named formula instead of silently averaging selected BMR results.
- Added a source-backed methodology table explaining best-use cases, inputs, and limitations for Mifflin–St Jeor, Harris–Benedict, Katch–McArdle, and Schofield.
- Added an indexable example BMR calculation, formula substitution, and moderate-activity TDEE example.
- Expanded the FAQ and FAQ schema for long-tail questions about BMR vs TDEE, BMR vs RMR, weight loss planning, lean mass, teenagers, pregnancy, units, and privacy.
Basal Metabolic Rate (BMR) is the energy your body uses just to keep you alive—breathing, circulation, temperature control, and basic organ function. This calculator estimates your resting calorie burn using several trusted equations, then lets you see a quick TDEE estimate by applying an activity multiplier.
How to use it
- Enter your sex, age, height, and weight, choosing metric or imperial units.
- Add body fat % if you know it for a lean-mass-based estimate.
- Select the formulas you want to compare.
- Choose the primary formula and activity level to view TDEE estimates.
- Use the results as a starting point for daily calorie planning.
When it’s useful
- Setting a baseline for weight maintenance, fat loss, or muscle gain goals.
- Comparing different BMR equations to see how estimates vary.
- Planning meal portions, calorie intake, or training phases.
- Tracking how changes in weight or body fat affect energy needs.
BMR formulas included
- Mifflin–St Jeor (1990): A common default for general use.
- Harris–Benedict (revised): A classic formula with updated coefficients.
- Katch–McArdle: Uses lean body mass when body fat % is known.
- Schofield: Uses age/sex-specific constants (often used by WHO/FAO).
Methodology: how this BMR calculator works
This calculator estimates basal metabolic rate using published predictive equations. Predictive equations are estimates, not lab measurements, and individual results can vary. For TDEE, the calculator multiplies one selected primary BMR formula by standard activity factors instead of averaging multiple formulas together.
| Formula | Best for | Inputs used | Important limitation |
|---|---|---|---|
| Mifflin–St Jeor | Default estimate for most adults | Sex, age, height, weight | Still an estimate; validation studies show individual error and underrepresentation in some age and ethnic groups. |
| Harris–Benedict, revised | Classic comparison formula | Sex, age, height, weight | Useful as a historical comparator, but it may differ from modern equations and measured energy expenditure. |
| Katch–McArdle | People who know body fat % | Weight and lean body mass | Only as accurate as the body-fat estimate used to derive lean body mass. |
| Schofield | Age/sex-based comparison | Age, sex, weight | Population averages; published error information still leaves substantial uncertainty for individuals. |
A systematic review by Frankenfield, Roth-Yousey, and Compher found Mifflin–St Jeor was the most reliable of four common predictive equations for estimating resting metabolic rate within 10% of measured values, while also noting important gaps and individual error. Schofield's work reports age- and sex-based equations using anthropometric measurements and includes error estimates. ACE describes Katch–McArdle as a lean-body-mass formula and lists the same activity multipliers used here for TDEE estimates.
Sources
- Mifflin–St Jeor equation: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990.
- Predictive equation accuracy: Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005.
- Revised Harris–Benedict equation: Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984.
- Schofield equation: Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr. 1985.
- Katch–McArdle, lean body mass, and activity multipliers: American Council on Exercise. Resting Metabolic Rate: Best Ways to Measure It and Raise It, Too.
- BMR vs RMR: American Council on Exercise. Basal Metabolic Rate vs Resting Metabolic Rate.
Equations (optional detail)
Mifflin–St Jeor (men): \( \mathrm{BMR} = 10w + 6.25h - 5a + 5 \)
Mifflin–St Jeor (women): \( \mathrm{BMR} = 10w + 6.25h - 5a - 161 \)
Harris–Benedict (revised) (men): \( \mathrm{BMR} = 88.362 + 13.397w + 4.799h - 5.677a \)
Harris–Benedict (revised) (women): \( \mathrm{BMR} = 447.593 + 9.247w + 3.098h - 4.330a \)
Katch–McArdle: \( \mathrm{BMR} = 370 + 21.6 \times \mathrm{LBM} \), where \( \mathrm{LBM} = w \times (1 - \mathrm{bf}) \)
Schofield: \( \mathrm{BMR} = A \times w + B \) (A and B depend on age group & sex).
Here \(w\) is weight in kg, \(h\) is height in cm, \(a\) is age in years, and \(\mathrm{bf}\) is body fat fraction.
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Frequently Asked Questions
What is a good BMR for my age?
There is no single “good” BMR for an age. BMR depends on height, weight, sex, lean mass, and other factors. It is better to compare your result with your own goals and TDEE than with a universal target.
Should I eat below my BMR to lose weight?
BMR is an estimate of resting energy needs, not a recommended calorie target. Many people plan weight loss from TDEE instead, using a moderate deficit and adjusting based on progress and wellbeing.
What is the difference between BMR and TDEE?
BMR estimates calories used at rest. TDEE estimates total daily calorie burn after adding activity.
What is the difference between BMR and RMR?
BMR is measured under stricter resting, fasted, temperature-neutral conditions. RMR is usually measured under less strict conditions and is often slightly higher.
Why do Mifflin–St Jeor and Harris–Benedict give different results?
They were derived from different datasets and coefficients. Mifflin–St Jeor is often used as a modern default, while Harris–Benedict remains a classic comparison formula.
When should I use Katch–McArdle?
Use it if you have a reasonably accurate body fat percentage, because the formula estimates BMR from lean body mass.
Can teenagers use this calculator?
Use caution. Adult BMR equations may not reflect growth and development needs. Teenagers should use age-appropriate guidance or professional advice.
Can I use this calculator during pregnancy or breastfeeding?
Use caution. Standard BMR equations do not fully account for pregnancy or lactation needs.
Why did my BMR go down after weight loss?
A smaller body usually needs less energy at rest. Loss of lean mass can also reduce resting energy needs.
Does muscle increase BMR?
More lean mass generally increases resting energy needs, which is why body composition affects BMR estimates.
Which formula should I use?
Mifflin–St Jeor is a solid default. If you know body fat %, Katch–McArdle personalizes the estimate using lean mass.
How do you compute TDEE?
TDEE = the selected primary formula's BMR × activity factor. We show a quick table using standard multipliers.
What units can I use?
Use centimeters or feet/inches for height and kilograms or pounds for weight. Toggle units in the form before calculating.
Is my data private?
Yes—everything runs locally in your browser. No uploads or storage.
At a glance
- BMR is the energy your body uses at rest for basic functions.
- TDEE is BMR adjusted for activity level.
- Mifflin–St Jeor is a strong default for most adults.
- Katch–McArdle may be useful if you know body fat percentage.
- All online BMR calculators are estimates, not medical measurements.
How accurate is a BMR calculator?
BMR equations are useful starting points, but they are based on population averages. Your actual resting energy use can differ because of body composition, genetics, age, hormones, medications, illness, sleep, and measurement error.
Editorial note
Created by Starlight Tools. Methodology last updated: June 2026.
This calculator is for educational planning only and is not medical, nutrition, or weight-loss advice. For personal guidance, consult a qualified clinician or registered dietitian.