Understanding your TDEE result
The activity multipliers below are the standard convention used with the Mifflin-St Jeor and Harris-Benedict equations. Choosing the right row matters more than any other input: two adjacent levels can differ by 300–400 kcal/day.
| Activity level | Multiplier | Typical description |
|---|---|---|
| Sedentary | 1.2 | Desk work, little or no deliberate exercise |
| Lightly active | 1.375 | Light exercise or sport 1–3 days per week |
| Moderately active | 1.55 | Moderate exercise 3–5 days per week |
| Active | 1.725 | Hard exercise 6–7 days per week |
| Very active | 1.9 | Very hard daily exercise or a physical job |
- Prediction equations estimate resting metabolism within about ±10% for most healthy adults; individual results can deviate further, particularly at very high or very low body weights.
- Self-reported activity level is the largest source of error in TDEE estimates. Many people select a higher category than their actual movement supports.
- The mild-deficit output is floored at 1,200 kcal/day (women) and 1,500 kcal/day (men). Calorie intakes below these levels fall into very-low-calorie-diet territory, which health agencies advise should only be undertaken with medical supervision.
- TDEE changes as body weight changes, so any estimate becomes outdated over time and should be recalculated periodically.
- A registered dietitian or healthcare professional can interpret energy needs in the context of individual health conditions, medications and goals.
What is TDEE?
Total Daily Energy Expenditure (TDEE) is the total number of calories a person expends in 24 hours. It is made up of resting metabolic rate (the energy the body uses at complete rest), the thermic effect of food (energy used to digest meals), and the energy cost of all movement, from formal exercise to fidgeting.
Because measuring energy expenditure directly requires laboratory methods such as indirect calorimetry or doubly labeled water, everyday tools estimate it instead. The most common approach — used by this calculator — is to estimate resting energy expenditure with the Mifflin-St Jeor equation (published in the American Journal of Clinical Nutrition in 1990) and multiply it by an activity factor between 1.2 (sedentary) and 1.9 (very active).
TDEE estimates carry meaningful uncertainty. The Mifflin-St Jeor equation predicts resting metabolic rate within about 10% of measured values for the majority of healthy adults, and self-selected activity multipliers add further error, because people commonly misjudge their own activity level. A TDEE figure is therefore a starting estimate to be checked against real-world data over several weeks, not a precise personal measurement.
How to use this TDEE calculator
- Select your sex and enter your age — both are variables in the Mifflin-St Jeor equation.
- Enter your weight and height, using the Metric/Imperial toggle if needed.
- Choose the activity level that best matches a typical week, counting occupational activity as well as exercise.
- Read your estimated TDEE together with the maintenance, mild-deficit and mild-surplus figures — results update instantly.
The formula behind TDEE
The calculator first estimates resting energy expenditure with the Mifflin-St Jeor equation (Mifflin & St Jeor et al., 1990), which validation studies — including a systematic review by the American Dietetic Association (Frankenfield et al., 2005) — found to be the most reliable of the common prediction equations for healthy adults.
The resting estimate is then multiplied by a standard activity factor: 1.2 for sedentary, 1.375 for light activity, 1.55 for moderate activity, 1.725 for active, and 1.9 for very active. Worked example: a 30-year-old male, 70 kg and 175 cm, has a Mifflin-St Jeor resting estimate of about 1,649 kcal/day; at the moderate multiplier of 1.55 this gives a TDEE of roughly 2,556 kcal/day.
The mild-deficit figure subtracts 500 kcal from maintenance and the mild-surplus figure adds 250 kcal. The deficit figure is never shown below 1,200 kcal/day for women or 1,500 kcal/day for men: health authorities including the NHS note that very-low-calorie diets below roughly these levels are not suitable for routine unsupervised use, because they make adequate nutrient intake difficult and are normally reserved for medically supervised programs. The calculator floors its output at these values for safety.
Common mistakes
- Overstating activity level — counting a physically inactive week as 'moderately active' inflates the estimate by several hundred kcal/day.
- Treating the TDEE number as exact rather than as a ±10% (or wider) starting estimate to verify against real-world trends.
- Confusing TDEE with BMR: BMR is resting metabolism only, while TDEE includes all daily activity.
- Not recalculating after body weight changes — energy expenditure falls as weight falls.
- Double-counting exercise by choosing a high activity multiplier and separately adding workout calories on top.
よくある質問
What is the difference between TDEE and BMR?
BMR (basal metabolic rate) is the energy the body uses at complete rest, while TDEE (total daily energy expenditure) is BMR plus the energy used for digestion and all physical activity. TDEE is calculated by multiplying a resting-energy estimate by an activity factor between 1.2 and 1.9, so TDEE is always higher than BMR.
How accurate is a TDEE calculator?
The Mifflin-St Jeor equation used here predicts resting metabolic rate within about 10% of laboratory-measured values for most healthy adults, according to the systematic review by Frankenfield and colleagues (2005). The activity multiplier adds additional uncertainty because activity level is self-assessed. TDEE calculators give a reasonable starting estimate, not a precise personal measurement.
Which activity level should I choose?
Choose based on a typical full week, including occupational activity. Sedentary means mostly sitting with little deliberate exercise; lightly active means exercise 1–3 days a week; moderately active means 3–5 days; active means hard exercise 6–7 days; very active means very hard daily training or a physically demanding job. When in doubt, most people with desk jobs and a few workouts per week fit the light-to-moderate range.
Why does the mild-deficit number stop at 1,200 or 1,500 kcal?
This calculator never displays a calorie target below 1,200 kcal/day for women or 1,500 kcal/day for men. Below roughly these levels an eating pattern enters very-low-calorie-diet territory, which health agencies such as the NHS state should only be followed under medical supervision because meeting nutrient needs becomes difficult. The floor is a safety guardrail, not a recommendation.
What are maintenance calories?
Maintenance calories are the daily energy intake at which body weight stays approximately stable — that is, intake equals total daily energy expenditure. In this calculator the maintenance figure equals the TDEE estimate. Actual maintenance intake varies between individuals and is best confirmed by tracking weight trends over several weeks.
Does TDEE change over time?
Yes. TDEE depends on body weight, body composition, age and activity, all of which change. Energy expenditure generally declines as weight decreases and as people age, and it rises with increased muscle mass or activity. Recalculating after any meaningful change in weight or routine keeps the estimate current.
参考文献
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 1990; 51(2): 241–247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association 2005; 105(5): 775–789.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th edition. Wolters Kluwer, 2021.
- NHS. Very low calorie diets. nhs.uk — guidance that VLCDs should be medically supervised.
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet 2011; 378(9793): 826–837.