Free calculator + calibration guide
Estimate your TDEE. Then test the estimate.
Use the Mifflin–St Jeor equation to build a responsible calorie range, then learn how consistent trend data turns population math into a useful personal starting point.
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The short version
- 1. Estimate resting energy with one visible equation.
- 2. Apply an honest activity range.
- 3. Calibrate against comparable trend data.
One public method
Mifflin–St Jeor
A widely used general-adult equation for estimating resting energy expenditure.
Male formula: 10 × kg + 6.25 × cm − 5 × age + 5
Female formula: 10 × kg + 6.25 × cm − 5 × age − 161
This estimates resting energy—not TDEE. The activity band below creates the working range.
Mechanism
What TDEE actually includes
Total daily energy expenditure is the energy your body uses across an entire day. Resting energy expenditure is the largest starting component, but structured exercise is only one piece of the total. Digestion, walking, standing, fidgeting, chores, physical work, and other daily movement also contribute.
Resting energy
The energy required to keep basic systems running at rest.
Thermic effect of food
The energy involved in digesting and processing food.
Exercise activity
Structured training and purposeful conditioning.
Non-exercise activity
Walking, standing, chores, fidgeting, and physical work.
Physique Skool Law: the formula starts the estimate; your observed trend decides whether the estimate deserves to stay.
Equation choice
Why this calculator uses Mifflin–St Jeor
Mifflin–St Jeor is a defensible, widely used general-adult starting equation. A 2005 systematic review found it was the most reliable of the common resting-metabolic-rate equations evaluated for broad use, while still documenting meaningful individual error. That final clause matters: a good population equation is still not a metabolic test.
The calculation has two visible steps
- 01
Mifflin–St Jeor estimates resting energy from weight, height, age, and the selected published sex-specific constant.
- 02
A behaviorally anchored activity band converts that resting estimate into a planning range. The band is an assumption that must be tested.
Newer Dietary Reference Intake models also publish direct energy-requirement equations built from doubly labeled water data. This version intentionally keeps one public path instead of presenting several formulas as if more choices guaranteed more accuracy. Those direct-TDEE models belong in a future controlled comparison—not a hidden selector on this calculator.
Interpretation
Where the estimate can drift
The equation can miss your true resting expenditure, and the activity band can miss the energy cost of your actual week. Reported body inputs, changing body mass, training load, work demands, and spontaneous movement add more uncertainty. Human energy expenditure can also adapt, so a rise in exercise does not always create a perfectly proportional rise in total expenditure.
Equation error
Population averages do not remove individual variation.
Activity error
A label cannot measure the movement in your real week.
Week-to-week change
Body mass, routine, and training demands do not stay fixed.
The calibration loop
The number starts the plan. The trend improves it.
- 01
Estimate
Choose a starting point inside the range.
- 02
Observe
Log intake and standardized weigh-ins.
- 03
Compare
Use weekly averages, not one reading.
- 04
Adjust
Change one main variable when justified.
- 05
Repeat
Run the same process with the new data.
Use comparable morning weigh-ins and a reasonably consistent intake record. Compare the average of days 1–7 with the average of days 8–14. Avoid grading the plan from one weigh-in or changing several inputs at once.
Fourteen days is a practical minimum for cleaner decisions, not a universal biological threshold. If travel, illness, training soreness, menstrual-cycle changes, or inconsistent logging make the trend noisy, extend the observation window to 21–28 days before changing course.
What to do Monday
Pick a starting target, define your weigh-in conditions, and decide now which two weekly averages you will compare. Consistency makes the result interpretable.
Limits and safety
When this calculator is not the right tool
This is educational guidance for adults, not medical nutrition therapy. Do not use it as the primary decision tool during pregnancy, under age 18, during an active eating disorder, during acute illness, or when a clinician has prescribed an energy intake.
Seek qualified assessment for rapid unexplained weight change, major metabolic disease, or medication effects that materially alter appetite, fluid balance, or metabolism.
Evidence boundary
Sources behind the estimate
The equation estimates resting energy in studied populations. The activity bands and calibration window are transparent coaching heuristics—not measured physiological constants. Your actual expenditure may fall outside the returned range.
- Mifflin et al. (1990) — original Mifflin–St Jeor resting-energy equation.
- Frankenfield et al. (2005) — systematic review comparing common resting-metabolic-rate equations.
- National Academies (2023) — current Dietary Reference Intake framework and direct energy-requirement equations.
- Westerterp (2017) — review of human energy expenditure, physical activity, and adaptation.
Practical takeaway
A useful estimate comes with a correction system.
Start with Mifflin–St Jeor, choose an honest activity band, collect comparable data, and adjust one main variable at a time. If you want the next self-serve layer, the free Starter Library organizes the training, nutrition, and recovery tools that follow this decision.
Get The Starter LibraryEducational only. This calculator is not a metabolic test, medical assessment, or promise of a particular outcome.