Updated September 2026 Total Daily Energy Expenditure — your maintenance calories based on the Mifflin-St Jeor formula
What is TDEE?
TDEE stands for Total Daily Energy Expenditure — the total number of calories your body burns in a 24-hour period. It includes your Basal Metabolic Rate (BMR), the thermic effect of food (about 10% of calories eaten), and all energy burned through physical activity and exercise.
TDEE is the most important number in nutrition science. Eat consistently below it and you’ll lose weight. Eat above it and you’ll gain. Match it exactly and your weight stays stable. Everything else — macros, meal timing, food quality — matters far less than this fundamental energy balance.
The Mifflin-St Jeor equation (used here) was validated in a 2005 study as the most accurate formula for estimating BMR in both obese and non-obese adults, outperforming the older Harris-Benedict equation.
How the TDEE calculation works, step by step
TDEE is not a single formula. It is a two-stage calculation: estimate your resting metabolism, then multiply it by how much you move. Both stages are shown below with real arithmetic, so you can reproduce the result by hand.
Stage 1 — the Mifflin-St Jeor equation
Published by Mifflin and St Jeor in 1990 and derived from 498 healthy adults, this equation predicts resting energy expenditure from four inputs. Weight is in kilograms, height in centimetres, age in years.
Women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161
The 166-calorie constant separating the two is not arbitrary — it reflects the average difference in lean body mass between men and women at a given height and weight. Lean tissue is what burns energy at rest, which is also why the equation is least accurate for people whose body composition is unusual for their size.
Stage 2 — the activity multiplier
Your BMR is then multiplied by a factor representing everything you do beyond lying still. These factors originate in the physical activity level ratios used by the FAO/WHO/UNU expert consultations.
| Factor | Level | What it describes |
|---|---|---|
| 1.2 | Sedentary | Desk job, no deliberate exercise, under ~5,000 steps |
| 1.375 | Lightly active | Light exercise 1–3 days a week, or 5,000–7,500 steps |
| 1.55 | Moderately active | Moderate exercise 3–5 days a week, or 7,500–10,000 steps |
| 1.725 | Very active | Hard exercise 6–7 days a week, or a physical job |
| 1.9 | Extremely active | Physical job plus daily training, or two sessions a day |
This second stage carries far more uncertainty than the first, and it is the one you choose yourself — which makes it the highest-leverage input in the whole calculation. Our guide to picking the right activity multiplier works through it using step count rather than self-assessment.
A full worked example
A 32-year-old woman, 68 kg, 167 cm, training three times a week and walking around 8,000 steps a day.
BMR = 680 + 1,043.75 − 160 − 161 = 1,402.75 kcal
TDEE = 1,402.75 × 1.55 = 2,174 kcal/day
To lose weight at a moderate pace she would eat roughly 20 percent below that — about 1,740 calories a day, projecting around 0.45 kg of loss per week. To gain, she would add 5 to 10 percent, or roughly 2,300 calories. Our guide to how fast you should lose weight explains why the deficit is expressed as a percentage rather than a fixed number.
How accurate is this number?
A 2005 review in the Journal of the American Dietetic Association compared the major predictive equations against measured resting metabolic rate and found Mifflin-St Jeor the most reliable, predicting within 10 percent of the measured value more often than the alternatives. Stated the other way round: roughly three in ten people fall outside that band, and a smaller group sits considerably further out.
Three sources of error stack up in a TDEE figure:
- The BMR equation — around ±10 percent, or ±140 calories on the example above. It cannot see your lean mass, so it under-predicts for muscular people and over-predicts for those with low muscle mass.
- The activity multiplier — easily ±25 percent, and by far the largest term. One level of misjudgement is worth several hundred calories a day.
- Day-to-day variation — your real expenditure moves with sleep, illness, ambient temperature and how much you fidget. It is a range, not a constant.
None of that makes the number useless; it makes it a starting hypothesis. See the BMR formula comparison for how six published equations differ on the same person.
Correcting it with your own data
After three weeks of consistent eating, your own body gives you a better figure than any equation. Hold your intake steady, weigh daily and average each week, then compare week three’s average with week one’s. Multiply the weekly change in kilograms by 7,700 and divide by seven — that is your true daily deficit or surplus. Add it back to your intake and you have your measured TDEE, which supersedes this calculator permanently.
Recalculate whenever your weight changes by 5 kg or your routine shifts. A smaller body costs less to run, which is why a target set at your starting weight quietly stops working — the most common cause of an apparent plateau.
TDEE calculator — FAQ
Recalculate every 4–8 weeks, or whenever your weight changes by more than 5 kg (10 lbs), your activity level changes significantly, or your results stop matching your goals. As you lose or gain weight, your TDEE changes — this is why recalculating regularly is important for continued progress.
Formula-based TDEE estimates are typically accurate within 10–15%, but individual variation is real. Factors like genetics, hormonal health, muscle mass, sleep, and stress all affect metabolism. If tracking calories at your TDEE for 3 weeks produces different results than expected, adjust your intake by 100–150 kcal and track for another 2 weeks.
Most people underestimate their activity level. If you have a physically demanding job (construction, nursing, waiting tables), choose “very active” even if you don’t exercise separately. If you sit most of the day but hit the gym 3–4 times a week, “lightly active” or “moderately active” is usually appropriate. When in doubt, start with a lower activity level and adjust up if you’re losing weight faster than expected.
Yes — TDEE and maintenance calories refer to the same thing: the number of calories that keeps your weight stable. Eating at your TDEE = weight maintenance. Eating below = weight loss. Eating above = weight gain. The relationship is approximately 7,700 calories per kilogram of fat (3,500 calories per pound).
They are the same number. TDEE is the physiological term for everything you burn in a day; “maintenance calories” is the practical name for eating that amount. Eat below it and you lose weight, above it and you gain.
Because they use different BMR equations and sometimes different activity factors. Harris-Benedict typically runs 60 to 80 calories above Mifflin-St Jeor, and Cunningham higher still. Our BMR formula comparison page shows six equations run on the same person so you can see the spread.
No — the activity multiplier in this calculation already includes your exercise. Adding tracker calories on top counts your training twice, and wrist-worn devices overestimate energy expenditure substantially in validation research.
Yes, and this is the most commonly missed point. Every kilogram lost reduces both your resting metabolism and the energy cost of moving. Recalculate every time your weight changes by about 5 kg, or your original deficit slowly disappears.