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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. 1. Estimate resting energy with one visible equation.
  2. 2. Apply an honest activity range.
  3. 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.

Working estimate

Build your calorie range

Units

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

  1. 01

    Mifflin–St Jeor estimates resting energy from weight, height, age, and the selected published sex-specific constant.

  2. 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.

  1. 01

    Estimate

    Choose a starting point inside the range.

  2. 02

    Observe

    Log intake and standardized weigh-ins.

  3. 03

    Compare

    Use weekly averages, not one reading.

  4. 04

    Adjust

    Change one main variable when justified.

  5. 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.

Book 1 §8.12 starts with fourteen days and an 80% adherence checkpoint. Below that checkpoint, fix execution and track for another week. If two comparable seven-day averages show flat or too-slow progress after checking intake and activity, review one roughly 100–200 kcal/day change and observe the next two weeks. Do not automatically wait a third week. These are coaching defaults; unclear or inadequate records or mismatched conditions require clarification, not an automatic calorie change or a fixed 21–28-day extension.

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.

Check the response before changing the target

This check belongs to stage 04, Response Control. First set Daily Targets, allocate the remainder, and design meals you can repeat.

Book 1 §8.12 starts with fourteen days, an 80% adherence checkpoint and roughly 100–200-calorie changes when flat or too-slow progress justifies one. These are the book’s coaching defaults.

The checks below determine whether the comparison is usable; they do not diagnose suitability or generate a personal prescription.

Is this a suitable self-directed adult nutrition plan?

Use qualified guidance for pregnancy or breastfeeding, an active eating disorder, acute illness, a prescribed medical diet, or concerning unexplained changes. This check does not assess those conditions.

Can you repeat the plan with a monitoring method that supports your wellbeing?

If tracking drives distress, compulsive behavior or harmful restriction, simplify the method and seek appropriate support. See Book 1 §8.11.

Was execution consistent enough for this protocol, with food and activity records you can interpret?

Include oils, drinks, weekends and changed activity. When using Book 1 §8.12, below 80% adherence means Not yet: fix execution and track for another week. The number is a coaching checkpoint, not proof that records above it are adequate.

Are the observations comparable enough to interpret the trend?

Use similar weighing conditions and review changes in intake, activity and water-related noise. A calendar deadline does not make mismatched observations comparable.

Is the declared review window complete, with enough usable observations?

Book 1 starts with fourteen days and two seven-day averages. Collect or clarify missing observations when necessary; do not automatically add a third week to an already interpretable comparison.

Are training performance, hunger and digestion still manageable?

If these have deteriorated, review delivery, recovery demands and the size of the diet change before making a further calorie cut. See §8.1 stage 04 and §8.13.

Does the repeated bodyweight trend match the intended goal?

Judge the agreed direction and rate from repeated observations, rather than a single reading. A flat trend can fit maintenance while missing a fat-loss goal.

Next step

Clarify this check first: Is this a suitable self-directed adult nutrition plan?

NIDDK adult-use boundary. Book source: §8.1 and §8.10–8.13. Answers stay in this page’s temporary state.

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.

  1. Mifflin et al. (1990) — original Mifflin–St Jeor resting-energy equation.
  2. Frankenfield et al. (2005) — systematic review comparing common resting-metabolic-rate equations.
  3. National Academies (2023) — current Dietary Reference Intake framework and direct energy-requirement equations.
  4. 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 Library

Educational only. This calculator is not a metabolic test, medical assessment, or promise of a particular outcome.