How TDEE is calculated
TDEE = BMR × activity factor
BMR comes from the Mifflin–St Jeor formula (see the BMR calculator). The activity factor scales it up for movement and exercise.
Activity factors
| Factor | Level |
|---|---|
| 1.2 | Sedentary (little or no exercise) |
| 1.375 | Lightly active (1–3 days a week) |
| 1.55 | Moderately active (3–5 days a week) |
| 1.725 | Very active (6–7 days a week) |
| 1.9 | Extra active (hard daily training or a physical job) |
- Sedentary: desk job, little planned exercise.
- Lightly active: light exercise or sports 1–3 days a week, or a job with some walking.
- Moderately active: moderate exercise 3–5 days a week.
- Very active: hard exercise 6–7 days a week.
- Extra active: very hard training, two sessions a day, or heavy physical work.
These multipliers are a widely used convention rather than results from one study. The FAO/WHO/UNU energy report describes lifestyles by physical activity level (PAL) on a similar scale, from about 1.4 for sedentary lifestyles to about 2.4 for very vigorous ones.
Worked example
A 30-year-old man, 180 cm and 80 kg, has a Mifflin–St Jeor BMR of 1,780 kcal. If he's moderately active:
TDEE = 1,780 × 1.55 = 2,759 kcal a day
Limitations
- If you're between two levels, the lower one gives a more cautious estimate.
- The result is a starting estimate. Tracking your weight for a few weeks tells you more about your real needs.
- It doesn't apply during pregnancy or breastfeeding, or for children and teens.
For anyone under 18, these calculators show a pointer to the CDC's BMI-for-age calculator and growth charts instead of adult results, because children and teens are still growing.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247.
- FAO/WHO/UNU. Human energy requirements (2004) — physical activity levels (PAL).
- 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;105:775–789.
- NIDDK (NIH): Body Weight Planner
Learn: How many calories should I eat a day? · BMR, RMR and TDEE explained