How to use this estimate
A TDEE number is most useful as a starting point to test, not a fact to obey. A practical way to use it:
- Follow a consistent intake for approximately 2–3 weeks.
- Track your average body weight over that time rather than reacting to any single day (day-to-day weight moves with water, sodium, and digestion, not just fat or muscle).
- Compare the observed trend with this estimate.
- Adjust gradually if your actual results differ from the estimate.
- Remember that changes in exercise, occupation, illness, sleep, medication, and body weight can all change your real energy needs over time.
BMR vs. TDEE — what is the difference?
Basal Metabolic Rate (BMR) is the energy your body would use over 24 hours at complete rest — breathing, circulation, cell repair, and other baseline processes. It typically accounts for the largest share of daily energy use for most people.
Total Daily Energy Expenditure (TDEE) starts from BMR and adds everything else: digesting food, incidental daily movement, and any structured exercise. TDEE is always equal to or greater than BMR, and the gap between the two is driven almost entirely by the activity factor.
Activity multipliers
Activity level is often the largest source of uncertainty in a TDEE estimate — two people with identical BMR can have real energy needs that differ by 50% or more once activity is factored in.
Activity levels, factors, and typical weekly patterns| Level | Factor | Typical pattern |
|---|
| Sedentary | 1.2 | Little structured exercise; mostly seated daily routine. |
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| Lightly active | 1.375 | Light exercise approximately 1–3 days per week. |
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| Moderately active | 1.55 | Moderate exercise approximately 3–5 days per week. |
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| Very active | 1.725 | Hard exercise approximately 6–7 days per week. |
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| Extra active | 1.9 | Very hard training, a highly physical occupation, or two-a-day training. |
|---|
Because this factor is an approximation of a whole week rather than a measurement, this calculator shows an estimated maintenance range (approximately ±10% around TDEE) instead of presenting one number as a perfectly precise target.
Worked example
Take a 30-year-old using the male reference equation, at 80 kg and 180 cm, who is moderately active (factor 1.55):
BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 cal/day
TDEE = 1,780 × 1.55 = 2,759 cal/day, displayed as 2,760 calories/day (rounded to the nearest 10), with an estimated maintenance range of roughly 2,480–3,030 calories/day.
For a gentle 10% weight-loss deficit, the daily target would be approximately 2,760 × 0.9 ≈ 2,480 calories/day — about 280 calories/day, or roughly 2,000 calories/week, below maintenance.
Limitations
TDEE and BMR estimates from any formula, including Mifflin-St Jeor, carry real uncertainty. This calculator’s estimate may be less representative for:
- Competitive and highly trained athletes, whose energy needs and body composition can differ substantially from the general adult population this formula was validated on.
- Pregnancy and breastfeeding, when energy needs change in ways this calculator does not model — see the FAQ below.
- People under 18, for whom this estimate is not intended (growing bodies have different, changing energy needs).
- People with diagnosed metabolic, thyroid, or hormonal conditions, medically supervised diets, or recent significant weight change, illness, or surgery — all of which can shift real energy needs away from a general-population formula.
- Anyone using prescription weight-management medication — this calculator must not be used to start, stop, or adjust any medication.
In every case, this tool provides an educational estimate to discuss with, not replace, a qualified healthcare professional or registered dietitian.
Sources and methodology
Formula: Mifflin-St Jeor resting energy expenditure equation, as published in the original clinical research below. Activity multipliers: the conventional 1.2–1.9 activity-factor approach commonly used alongside Mifflin-St Jeor, clearly labelled here as an approximation. Safety and limitations: informed by CDC and NIH/NIDDK public health guidance on energy needs and healthy weight, cited below.
This calculator implements the published Mifflin-St Jeor formula and the conventional activity-factor approach; it is an independent implementation and is not affiliated with, endorsed by, or a reproduction of the NIH Body Weight Planner or any other named tool.