BMR/TDEE Calculator: Mifflin-St Jeor Guide
Estimate BMR and TDEE with the Mifflin–St Jeor equation. See a worked example, activity factors, input limits, calibration steps, and practical safety notes.
BMR estimates the energy used to maintain basic functions at rest. TDEE adds an activity assumption to estimate total daily expenditure. Enter biological sex, age, height, weight, and activity level in the online BMR/TDEE calculator to get results in kilocalories per day. Use them as an adult tracking baseline, not a nutrition prescription.
Worked BMR and TDEE Calculator Example
The page defaults to a 30-year-old male who is 170 centimeters tall and weighs 65 kilograms. “Moderate activity” is selected, giving an activity factor of 1.55.
First apply the male Mifflin–St Jeor equation:
BMR = 10 × 65 + 6.25 × 170 − 5 × 30 + 5
= 1567.5 kcal/day
The page rounds the displayed result to 1568 kcal/day. TDEE is then calculated with the activity factor:
TDEE = 1567.5 × 1.55
= 2429.625 kcal/day
The displayed TDEE is approximately 2430 kcal/day.
This does not mean that eating exactly 2430 kilocalories will guarantee a constant body weight. The equation and activity factor are estimates. Body composition, non-exercise activity, training, sleep, illness, medication, and tracking error can all move actual expenditure away from the result.
What Is the Difference Between BMR and TDEE?
The difference is the scope of each estimate:
| Metric | Question it answers | Method used here |
|---|---|---|
| BMR | How much energy might basic functions use at rest? | Mifflin–St Jeor prediction equation |
| TDEE | How much energy might be used over a day at the selected activity level? | BMR × activity factor |
Technically, the 1990 paper by Mifflin and colleagues developed an equation for resting energy expenditure, or REE. It was derived from 498 healthy adults whose REE was measured with indirect calorimetry. [1] Everyday calculators often label the equation output BMR, and this page follows that convention. A predicted result is not the same as BMR or REE measured under controlled conditions.
An NCBI energy-balance reference describes total energy expenditure as including basal or resting metabolism, physical activity, and the thermic effect of food. [2] This calculator compresses day-to-day variation into one activity multiplier, so its TDEE is a starting estimate rather than a measurement.
The Mifflin–St Jeor Equations
The calculator expects weight in kilograms, height in centimeters, and age in complete years.
For males:
BMR = 10 × weight + 6.25 × height − 5 × age + 5
For females:
BMR = 10 × weight + 6.25 × height − 5 × age − 161
Change only the biological-sex selection in the default example to female:
BMR = 10 × 65 + 6.25 × 170 − 5 × 30 − 161
= 1401.5 kcal/day
TDEE = 1401.5 × 1.55
≈ 2172 kcal/day on the page
The different constants are part of the original prediction model. Sex alone does not fully describe individual metabolism; body composition, health, and actual activity can still produce a different measured expenditure.
Use the age and date interval calculator if you need to confirm complete age. If height or weight is recorded in imperial units, convert feet, inches, or pounds first with the common unit converter.
How to Choose an Activity Factor
The page provides five fixed activity levels:
| Page option | Factor | Page description |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise |
| Light activity | 1.375 | Exercise 1–3 days per week |
| Moderate activity | 1.55 | Exercise 3–5 days per week |
| High activity | 1.725 | Exercise 6–7 days per week |
| Very high activity | 1.9 | Physical work or intense training |
These factors are fixed assumptions used by this page's TDEE model. They are not part of the original Mifflin–St Jeor paper. Choose the option closest to a sustained routine, not the hardest workout completed on one unusual day.
Non-exercise activity matters too. Commuting, standing, housework, walking, and physical employment all contribute to daily expenditure. Two people with the same training schedule can have different actual TDEE because the rest of their days differ.
If no option feels exact, start with the most conservative reasonable level and treat its result as a hypothesis. Calibrating against a consistent trend is more useful than repeatedly selecting a more flattering multiplier.
Use the Online BMR/TDEE Calculator in Three Steps
- Open the BMR/TDEE calculator
- Enter biological sex, age, height, and weight, then choose a long-term activity level
- Record the BMR, activity factor, TDEE, inputs, and date
Results update whenever an input changes. “Reset example” restores male, age 30, 170 centimeters, 65 kilograms, and moderate activity.
The accepted input ranges are:
- Age: 18–120 years
- Height: 100–250 centimeters
- Weight: 25–350 kilograms
- Activity: one of the five preset factors
An empty, non-finite, or out-of-range value clears the result and displays a validation message. Age, height, and weight are processed only in the current browser and are not uploaded by this tool.
Calibrate TDEE with a Multiweek Trend
Do not treat the first result as a permanent target. Treat it as an initial hypothesis. Keep measurement conditions reasonably consistent, then compare average weight trends, intake records, and activity changes across several weeks before deciding whether the estimate is persistently high or low.
A practical sequence is:
- Save one set of inputs, activity level, and initial TDEE
- Record weight under similar conditions without reacting to a single day's movement
- Track food, training, steps, sleep, and major routine changes
- Review a multiweek trend, then adjust the assumption modestly or consult a professional
The NIH/NIDDK Body Weight Planner uses a dynamic model for goal weight, time, and activity changes. It also warns that its values may be too high for people with abnormally low metabolism or very sedentary routines. [3] A static BMR-times-factor calculation is therefore not designed to predict complex long-term weight change.
The percentage calculator can measure the change between two recorded weights or intake values. BMI answers a different question; use the BMI calculator if you need the Chinese adult height-and-weight screening category.
Who Should Not Use the Result as a Calorie Target?
This page is intended as an everyday estimate for adults aged 18 and older. Do not directly turn it into an intake target for:
- Minors
- Pregnancy or breastfeeding
- Conditions that affect metabolism, absorption, or energy requirements
- Medication changes that may affect weight or metabolism
- A history or suspected risk of an eating disorder
- Competitive training, postoperative recovery, or clinical nutrition support
Those situations may require different equations, examination, and follow-up. Ask a physician, registered dietitian, or another qualified professional instead of changing intake from an online estimate alone.
Frequently Asked Questions
Is BMR the Minimum Number of Calories I Must Eat?
That is not what BMR means. It predicts resting energy expenditure; it does not automatically prescribe a minimum intake. An intake plan must consider total expenditure, nutrients, health, goals, and professional assessment.
Is TDEE a Weight-Loss Calorie Target?
No. This page uses TDEE as an estimated maintenance starting point. A weight-loss or weight-gain plan also needs an appropriate rate, health-risk review, food quality, training context, and observed trend. One TDEE result cannot choose the plan.
Why Does My Watch Show a Different Calorie Number?
Both are model estimates with different inputs and algorithms. A wearable may use heart rate, steps, and exercise records. This page uses sex, age, height, weight, and a fixed activity factor. A disagreement does not prove that either number is exact.
How Much Can the Activity Factor Change the Result?
It depends on BMR. In the default male example, BMR is 1567.5 kcal/day. Moving from the sedentary factor of 1.2 to the moderate factor of 1.55 increases estimated TDEE by about 549 kcal/day. That is a model difference, which is why the activity category should not be chosen casually.
Why Are Results Rounded?
The page displays BMR and TDEE as the nearest whole kilocalorie. It keeps the full BMR value for the TDEE calculation and formats only the displayed results. Rounding BMR too early by hand can therefore create a difference of roughly one kilocalorie.
How to Interpret the Result
Treat BMR and TDEE as testable starting assumptions: record the inputs, watch the trend, and revise when the evidence changes. A value displayed to the nearest kilocalorie does not mean the body follows a precise daily allowance. Seek qualified help when health conditions, rapid weight change, or a structured nutrition plan is involved.