BMR is the calories you burn at rest; TDEE is the calories you burn in a day, activity included. For a 35-year-old woman weighing 70 kg, BMR is 1,395 calories a day and lightly active TDEE is 1,918 — a 523-calorie gap covering everything beyond lying still. Use BMR as your floor and TDEE as your planning number.
People mix the two up constantly, and the mix-up has real consequences: eat at your BMR when you meant your TDEE and you will be hundreds of calories short every day.
What Is BMR?
BMR — basal metabolic rate — is the energy your body needs to run its basic, life-sustaining functions while completely at rest: breathing, circulating blood, keeping your organs working, and maintaining body temperature. It is measured under strict laboratory conditions: lying still, awake, in a warm room, after an overnight fast.
Your BMR is the biggest single slice of your daily burn, usually 60 to 70 percent of the total. The standard way to estimate it is the Mifflin-St Jeor formula, published in 1990. For women it is (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. Our example woman — 35 years old, 70 kg, 165 cm — works out to 10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031.25 − 175 − 161 = 1,395 calories a day. If that is new to you, our guide to what BMR is covers it in full, and a free bmr calculator gives you your own figure in seconds.
What Is TDEE?
TDEE — total daily energy expenditure — is the total number of calories you burn in a full day, including everything BMR covers plus everything else. It has four components:
- BMR (60–70 percent of the total). The resting burn described above.
- Thermic effect of food (about 10 percent). The energy spent digesting and processing what you eat. Protein costs the most to digest — 20 to 30 percent of its calories are burned in processing, against 5 to 10 percent for carbohydrates and 0 to 3 percent for fat.
- Exercise activity. Planned workouts: running, lifting, classes, sport.
- NEAT — non-exercise activity thermogenesis. Everything else you do while awake: walking to the shops, taking the stairs, standing, cleaning, fidgeting. NEAT varies enormously between people and can account for differences of 100 to 800 calories a day between two people of similar size.
In practice, TDEE is estimated by multiplying BMR by an activity factor, which rolls the last three components into one number:
| Activity level | What it looks like | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days a week | 1.375 |
| Moderately active | Moderate exercise 3–5 days a week | 1.55 |
| Very active | Hard exercise 6–7 days a week | 1.725 |
| Extremely active | Physical job plus daily training | 1.9 |
That single multiplier is doing a lot of work, which is why honesty about your activity level matters so much — it is the biggest source of error in the whole calculation.
BMR vs TDEE at a Glance
| BMR | TDEE | |
|---|---|---|
| What it measures | Calories burned at complete rest | Calories burned in a full real day |
| What it includes | Breathing, circulation, organ function, body temperature | BMR + digestion + exercise + all daily movement |
| Typical size | 60–70% of daily burn | 100% of daily burn |
| Our example woman | 1,395 calories a day | 1,918 (lightly active) |
| Changes with | Age, sex, weight, height, muscle mass | All of the above, plus activity level |
| Used for | A floor — never eat below it for long | Planning — eat below it to lose, above it to gain |
The two numbers answer different questions. BMR answers “what does my body cost to keep alive?” TDEE answers “what does my day actually cost?” Only the second one tells you how much to eat.
Worked Example: One Woman, Both Numbers
Take the same 35-year-old woman — 70 kg, 165 cm, 28 percent body fat — and hold her BMR fixed at 1,395 while her activity changes. Her TDEE at each level is her BMR times the multiplier:
- Sedentary (× 1.2): 1,395 × 1.2 = 1,674 calories a day
- Lightly active (× 1.375): 1,395 × 1.375 = 1,918 calories a day
- Moderately active (× 1.55): 1,395 × 1.55 = 2,163 calories a day
- Very active (× 1.725): 1,395 × 1.725 = 2,407 calories a day
- Extremely active (× 1.9): 1,395 × 1.9 = 2,651 calories a day
Same woman, same BMR — nearly a 1,000-calorie range in TDEE, from 1,674 to 2,651. That range is why two people with identical BMRs can need completely different diets, and why the formula choice (Mifflin-St Jeor’s 1,395 versus Katch-McArdle’s 1,459 or Harris-Benedict’s 1,466 for this woman) is a footnote by comparison: those three disagree by at most 71 calories, while the activity choice moves the answer by hundreds. If you want to check the arithmetic yourself, our guide to how to calculate BMR works through every step by hand.
Which One Do You Use to Lose Weight?
Use TDEE. Weight loss comes from eating below your TDEE, not below your BMR. The standard approach is a deficit of 300 to 500 calories a day below TDEE, which predicts roughly 0.5 to 1 pound a week, since a pound of body fat stores about 3,500 calories.
For our example woman at lightly active (TDEE 1,918):
- Maintain: eat about 1,918 calories a day
- Lose about 0.5 lb a week: eat about 1,668 (a 250-calorie deficit)
- Lose about 1 lb a week: eat about 1,418 (a 500-calorie deficit)
- Gain weight: eat about 2,200 or more (a surplus above TDEE)
Notice that even her 1-pound-a-week target of 1,418 sits above her BMR of 1,395. That is how it should be. Eating below BMR for more than a short stretch forces your body to cut corners on muscle, energy, and hormone function. Most health guidance also sets about 1,200 calories a day for women and 1,500 for men as the floor for unsupervised dieting. A free basal metabolic rate calculator shows your BMR and TDEE side by side so you can see both before choosing a target, and our calorie calculator turns the pair into a daily eating plan. For the other half of the picture, check your body mass index with our free BMI calculator.
Why People Confuse BMR and TDEE
Three traps cause most of the confusion. The first is language: fitness apps and watches often label a number “calories burned” or “resting calories” without saying whether activity is included, so users compare a BMR from one app with a TDEE from another and conclude one of them is broken. The second is the activity multiplier itself — most people pick one level too high, which inflates TDEE and quietly erases their deficit. If you sit most of the day and walk the dog in the evening, you are lightly active, not moderately active. The third is treating the formulas as exact: every BMR figure is an estimate, usually within about 10 percent of the true value, so a calculator that says 1,395 really means “roughly 1,300 to 1,500.” The fix for all three traps is the same: track your weight for two to three weeks at a steady intake. If it is stable, your intake equals your real TDEE whatever the formula said. If it is falling by about a pound a week, you are in roughly a 500-calorie deficit. The scale calibrates the formula — not the other way round.
BMR, TDEE, and Body Fat
One more distinction matters for this calculator in particular. BMR formulas that use total body weight treat a kilogram of fat and a kilogram of muscle as the same thing, which they are not: muscle burns roughly 6 calories per pound per day at rest, fat only about 2. For our example woman at 28 percent body fat, lean mass is 70 × (1 − 0.28) = 50.4 kg, and Katch-McArdle gives 370 + 21.6 × 50.4 = 1,459 calories a day, 64 above her Mifflin-St Jeor figure. With a body fat percentage, the body fat calculator on the same page lets the formula work from lean mass instead of total weight. If you are very lean or very muscular, that lean-mass version is the BMR worth using — and your TDEE follows from it in exactly the same way, by multiplying by your activity factor.
FAQ: BMR vs TDEE
Is TDEE higher than BMR?
Yes, always. TDEE equals BMR plus the calories spent digesting food, exercising, and moving through the day. For a lightly active person, TDEE is typically about 1.375 times BMR — 1,918 versus 1,395 for our example woman.
Should I eat my BMR or my TDEE to lose weight?
Eat below your TDEE, not below your BMR. A deficit of 300 to 500 calories under TDEE is the standard approach. Eating at or below BMR for long stretches risks muscle loss, fatigue, and hormonal disruption.
Can BMR and TDEE be the same number?
Only if you never moved at all — in practice, no. Even a fully sedentary day includes getting up, eating, and moving around the house, which is why the lowest activity multiplier is 1.2, not 1.0.
Why is my TDEE different on different calculators?
Mostly because of the activity multiplier: different tools describe the levels differently, and a one-level difference changes the answer by 200 to 300 calories. The BMR formula matters far less — Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle usually agree within about 100 calories.
Does exercise change my BMR or my TDEE?
Exercise changes your TDEE immediately, because it adds activity calories. It changes your BMR only slowly, by building muscle — each pound of muscle adds roughly 6 calories a day to your resting burn.
What if my weight does not change at my calculated TDEE?
Then your real TDEE is close to your intake, and the formula overestimated your activity. Drop the multiplier one level and retest for two to three weeks, or reduce intake by 200 to 300 calories and watch the trend.