Every nutrition decision you make, whether you want to lose fat, build muscle or simply stop guessing, starts with one number: your Total Daily Energy Expenditure (TDEE). TDEE is the total number of calories your body burns in a 24-hour period. Eat at your TDEE and your weight stays roughly stable. Eat below it and you lose weight; eat above it and you gain. This guide explains exactly what makes up that number, how calculators estimate it, why the estimate is only a starting point, and how to use two to three weeks of real-world data to find your true maintenance calories.
What is TDEE?
TDEE is not a single process. It is the sum of four distinct components, each of which you can influence to a different degree. Researchers usually break it down like this:
| Component | What it is | Share of TDEE |
|---|---|---|
| BMR / RMR | Energy to keep you alive at rest: breathing, circulation, organ function | 60–70% |
| NEAT | Non-exercise activity: walking, fidgeting, standing, chores | 15–30% (highly variable) |
| EAT | Exercise activity thermogenesis: planned workouts | 5–10% |
| TEF | Thermic effect of food: energy used to digest and absorb food | ~10% |
Two points stand out. First, your resting metabolism is by far the largest piece, and it is mostly determined by body size and lean mass. Second, NEAT, not gym time, is the component that varies most between people. Levine and colleagues showed that NEAT can differ by up to 2,000 kcal per day between individuals of similar size, and that people who resist fat gain during overfeeding tend to unconsciously increase NEAT [1].
How BMR is estimated: the equations compared
Measuring resting metabolic rate directly requires indirect calorimetry in a lab. For everyone else, predictive equations estimate it from sex, age, weight and height. The most common options are:
| Equation | Year | Inputs | Notes |
|---|---|---|---|
| Harris-Benedict (revised) | 1984 | Sex, age, weight, height | Tends to overestimate in modern populations |
| Mifflin-St Jeor | 1990 | Sex, age, weight, height | Most accurate for most adults in validation studies |
| Katch-McArdle | 1996 | Lean body mass | Good for lean, athletic people with a known body fat % |
A systematic review by Frankenfield and colleagues for the American Dietetic Association found the Mifflin-St Jeor equation predicted resting metabolic rate within ±10% of measured values in more non-obese and obese adults than any other equation tested [2]. That is why our TDEE calculator uses it by default. The formula is:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
If you know your body fat percentage (you can estimate it with our body fat calculator), Katch-McArdle can be more accurate for very muscular people, because it bases the estimate on lean mass rather than total weight: BMR = 370 + 21.6 × lean mass (kg).
From BMR to TDEE: activity multipliers
Once BMR is estimated, calculators multiply it by an activity factor to account for NEAT, exercise and TEF together. These factors come from doubly labelled water studies that measured real-world energy expenditure as a multiple of BMR (the "physical activity level", or PAL).
| Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise, under ~5,000 steps | 1.2 |
| Lightly active | Light exercise 1–3 days/week or ~5–7,500 steps | 1.375 |
| Moderately active | Moderate exercise 3–5 days/week or ~7,500–10,000 steps | 1.55 |
| Very active | Hard exercise 6–7 days/week or physical job | 1.725 |
| Athlete | Twice-daily training or very heavy manual labour | 1.9 |
A worked example
A 35-year-old woman, 168 cm, 72 kg, who lifts three times a week and walks about 7,000 steps a day: BMR = 10 × 72 + 6.25 × 168 − 5 × 35 − 161 = 720 + 1,050 − 175 − 161 = 1,434 kcal. With a lightly active multiplier of 1.375, her estimated TDEE is about 1,970 kcal per day.
Why your calculated TDEE is only an estimate
Even the best equation describes an average person of your size. Individual metabolic rates for people of the same weight, height and age can differ by several hundred calories, because of differences in lean mass, organ size, genetics, hormones and NEAT. Add normal errors in food logging (people underreport intake by 10–45% in studies) and it is clear that a calculator gives you a well-informed starting point, not a final answer.
How to find your true maintenance calories
The most reliable way to find your real TDEE is to treat the calculator result as a hypothesis and test it with your own data. Here is a simple protocol:
- Calculate your estimate with the TDEE calculator.
- Eat consistently at that number for 14–21 days, logging food as accurately as you can (a digital kitchen scale helps).
- Weigh yourself every morning after using the bathroom, before eating, and record the 7-day average rather than single readings.
- Compare the first weekly average with the last. If the change is under ±0.2 kg (0.5 lb) per week, you have found maintenance.
- If you are gaining or losing, adjust: each 0.5 kg (1.1 lb) of weekly change corresponds to roughly 550 kcal per day. Change intake by that amount and repeat.
This adaptive approach is how most coaches work, and it automatically corrects for logging errors, because you keep using the same logging method.
How TDEE changes over time
Your TDEE is not fixed. As you lose weight, you have less tissue to maintain and move, so BMR and the energy cost of activity both fall. Research also shows that energy expenditure can drop slightly more than predicted from weight loss alone, a phenomenon called adaptive thermogenesis [3]. We cover this in depth in our guide to metabolic adaptation and refeeds. In practice, recalculate your TDEE after every 4–5 kg (10 lb) of weight change, and whenever your activity level changes substantially.
Putting your TDEE to work
Once you know your maintenance calories, the next steps depend on your goal:
- Fat loss: subtract 300–500 kcal for a sustainable deficit. Read Calorie Deficit 101 to protect muscle along the way.
- Muscle gain: add 200–300 kcal for a lean bulk.
- Recomposition: eat near maintenance with high protein and progressive strength training.
- Macros: split your target calories into protein, carbs and fat with the macro calculator.
- Timeline: see when you could reach your goal weight with the goal date calculator.
Key takeaways
- TDEE = BMR + NEAT + exercise + thermic effect of food.
- Mifflin-St Jeor is the most accurate general-purpose BMR equation for most adults.
- Choose a conservative activity multiplier; most people overestimate.
- Use 2–3 weeks of weight trend data to turn the estimate into your true maintenance.
- Recalculate after every 4–5 kg of weight change.
Put this into practice
Calculate your TDEE →References
- Levine JA, Eberhardt NL, Jensen MD. Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science. 1999;283(5399):212–214.
- 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(5):775–789.
- Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. Int J Obes. 2010;34(Suppl 1):S47–S55.
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247.
Educational content only, not medical advice. See our medical disclaimer.