What is the difference between BMR and TDEE?

BMR (basal metabolic rate) is the energy your body burns at complete rest just to stay alive — running your heart, brain, lungs, and other organs. TDEE (total daily energy expenditure) is your whole day's burn: your BMR plus the calories used for digestion, everyday movement, and exercise. You find TDEE by multiplying BMR by an activity factor of roughly 1.2 to 1.9, so TDEE is always larger than BMR. TDEE is your maintenance calorie level.

Is RMR the same as BMR?

Almost, but not exactly. BMR is measured under strict lab conditions — after an overnight fast, fully rested, lying still in a controlled room. RMR (resting metabolic rate) is measured under looser conditions, so it runs about 10% higher than true BMR. The two are close enough to be used interchangeably, and the standard prediction formulas actually estimate RMR in practice while being labelled as BMR calculators.

Which number should I use to lose weight?

Use your TDEE (maintenance calories) as the starting point, then subtract a deficit. For example, if your TDEE is about 2,200 kcal, eating around 1,700 kcal creates a 500 kcal daily deficit for steady loss of roughly 1 lb (0.45 kg) a week. Don't build a target around your BMR, and avoid eating below your BMR for long stretches — that's the energy your organs need at rest, and chronically under-eating it is hard to sustain.

How accurate are BMR and TDEE calculators?

For most healthy adults, a Mifflin-St Jeor BMR estimate lands within about 10% of a lab measurement — a 2005 systematic review found it accurate to within 10% for roughly 82% of non-obese people, more than any competing formula. TDEE adds more uncertainty because the activity factor is a self-chosen guess. Treat any figure as an informed starting point, then let two to three weeks of weight-trend data fine-tune it.

Why is my TDEE so much higher than my BMR?

Because TDEE includes everything you do on top of resting. BMR is typically 60-70% of your daily burn; the rest comes from the thermic effect of food (about 10%, used digesting meals) and physical activity — both structured exercise and non-exercise movement like walking, standing, and fidgeting (NEAT). Someone active and on their feet all day can have a TDEE far above their BMR, while a desk-bound day adds much less.

BMR vs TDEE vs RMR: What's the Difference?

BMR is the calories your body burns at complete rest, RMR is nearly the same number measured under looser conditions (about 10% higher), and TDEE is your whole day's burn — your resting rate multiplied by an activity factor. Put simply: BMR and RMR describe your body ticking over, while TDEE is what you actually spend once you add movement, exercise, and digestion. TDEE is your maintenance calorie level — the number most weight goals are built around — so if you remember one figure, remember that one. Here is how the three connect and which to use for what.

BMR: energy at complete rest

Your basal metabolic rate (BMR) is the calories your body needs just to stay alive while doing nothing — keeping your heart beating, lungs breathing, brain firing, kidneys filtering, and temperature steady. For most people this is the largest slice of daily energy use, usually around 60-70% of the total.

The word "basal" is strict. A true BMR is measured in a lab after an overnight fast (10-12 hours), fully rested, lying still and awake in a thermally neutral room, with no recent exercise. Those conditions strip out everything except the baseline cost of being alive. Because that setup is impractical outside research, few people ever have their genuine BMR measured.

RMR: the same idea, measured more loosely

Resting metabolic rate (RMR) answers the same question — how many calories do you burn at rest? — but under relaxed conditions: awake and resting, without the strict fast or controlled room a true BMR demands. Because a little residual digestion and movement creeps in, RMR typically runs about 10% higher than BMR.

In everyday use the two terms are treated as interchangeable, and that is mostly fine. One useful subtlety: the popular prediction equations were validated against resting measurements, so a formula labelled a "BMR calculator" is really predicting your RMR. You can find your BMR with our calculator — just know the output sits at that practical resting level, not a strict lab-basal figure.

The Mifflin-St Jeor equation

The modern standard for estimating resting energy is the Mifflin-St Jeor equation, published in 1990. It uses weight, height, age, and sex:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

A 35-year-old man of 175 cm and 80 kg (5 ft 9 in, 176 lb) works out to about 1,720 kcal/day at rest. Mifflin-St Jeor replaced the older 1919 Harris-Benedict formula because it fits modern bodies better: a 2005 systematic review found it predicts measured resting metabolism to within 10% for about 82% of non-obese adults — more people than any competing equation. Despite the "BMR" label, what it predicts in practice is your RMR, which is why the small BMR/RMR gap rarely matters for planning.

No formula is perfect. Muscle mass, genetics, age, and ethnicity all shift resting metabolism, and equations based on total body weight tend to overestimate for people carrying a lot of fat. Read any estimate as an informed starting point, not a measurement.

TDEE: your whole-day burn

Your total daily energy expenditure (TDEE) is everything you burn in 24 hours — rest plus all activity. The quick calculation is:

TDEE = BMR × activity factor, where the factor runs from about 1.2 (sedentary) to 1.9 (very active).

That single multiplier bundles together four components stacked on your resting rate:

BMR/RMR — the resting baseline, about 60-70% of the total.
Thermic effect of food (TEF) — energy spent digesting and processing meals, roughly 10% of what you eat.
Exercise activity — deliberate training: runs, lifts, classes, sport.
NEAT (non-exercise activity thermogenesis) — the incidental movement of daily life: walking, standing, chores, fidgeting. NEAT varies enormously between people and can swing daily burn by hundreds of calories.

Because the activity factor already includes exercise, NEAT, and TEF, TDEE is your maintenance level — eat that many calories and your weight holds roughly steady. Estimate yours by using our tool to find your maintenance calories.

Activity levels and multipliers

Choosing an activity factor is where most people go wrong, usually by picking too high. The multiplier should reflect an average week, not your best one, and it already includes your workouts — so there is no need to add calories back for exercise on top.

Activity level	Multiplier	What it means
Sedentary	× 1.2	Desk job, little or no deliberate exercise
Lightly active	× 1.375	Light exercise or sport 1-3 days a week
Moderately active	× 1.55	Moderate exercise 3-5 days a week
Very active	× 1.725	Hard exercise 6-7 days a week
Extra active	× 1.9	Physical job or twice-daily / very intense training

Standard TDEE activity multipliers. Example: a 1,720 kcal BMR at "moderately active" (× 1.55) gives a TDEE of about 2,670 kcal/day. When in doubt, pick the lower band — overestimating activity is the most common reason a calorie plan quietly stops working.

Which number should you use?

Now the practical part — matching each figure to a goal:

For any calorie target, start from TDEE. Your maintenance level is the reference point for every goal: eat below it to lose, above it to gain, at it to maintain. If your TDEE is 2,200 kcal, a 500 kcal deficit means eating about 1,700 kcal for a steady loss of roughly 1 lb (0.45 kg) per week. You can turn a maintenance number straight into a target with our calorie deficit calculator.
Use BMR as a floor, not a target. BMR tells you the minimum energy your organs need at rest. Don't sit below your BMR for long stretches: chronically under-eating your resting needs leaves nothing for daily activity, is hard to sustain, and tends to worsen fatigue, mood, and adherence — often stalling the progress you are chasing. If a deficit pushes you under BMR, shrink the deficit or add activity instead.
Treat RMR as effectively your BMR for planning. Unless you have had a lab measurement, the resting number from a calculator serves both roles.

The whole thing fits in one line: BMR (or RMR) is the floor, TDEE is the target. Build the plan on TDEE, and use BMR only to check you are not cutting too far.

How accurate are these estimates?

Every number here is a prediction, and the honest expectation is within about 10% — sometimes closer, occasionally further. Two errors stack. The equation itself carries a modest error for any individual, since body composition and genetics vary. On top of that, the activity factor is a self-assigned guess, and small misjudgements there move TDEE more than the formula ever will.

That is not a reason to distrust the tools — it is a reason to use them well. Take your calculated TDEE as a starting hypothesis, eat at it (or at your chosen deficit) for two to three weeks, and watch the multi-week weight trend rather than daily swings, which mostly reflect water and food volume. If the trend is not moving the way your goal needs, adjust by 100-200 kcal and reassess. Your own results always beat any equation.

Putting it together

To recap in one line: BMR is rest, RMR is rest measured loosely (~10% higher), and TDEE is BMR × an activity factor of 1.2 to 1.9 — which equals your maintenance calories. Estimate your resting rate with Mifflin-St Jeor, layer on an honest activity multiplier to get TDEE, build your calorie target from that TDEE, and keep BMR in mind as a floor you should not dip below for long. This is general information for healthy adults, not medical advice; if you are pregnant or breastfeeding, managing a medical condition, or under a clinician's care, check with a professional before making big changes to how much you eat.

Sources

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990 — the original Mifflin-St Jeor equation.
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 — accuracy within ~10% for ~82% of non-obese adults.
FAO/WHO/UNU. Human Energy Requirements (physical activity levels / PAL) — basis for the activity-factor ranges.
CDC — Healthy Weight and steady weight loss.
NHS — Healthy weight and calorie guidance.
NIH / NIDDK — Weight management.
ISSN — Position stand: diets and body composition (J Int Soc Sports Nutr, 2017) — TDEE components including TEF and NEAT.
Levine JA. Non-exercise activity thermogenesis (NEAT). Endotext, NCBI Bookshelf.

Key sources: the Mifflin-St Jeor resting-energy equation (Am J Clin Nutr, 1990); the Frankenfield 2005 systematic review on equation accuracy (~10% for ~82% of non-obese adults); FAO/WHO/UNU human energy requirements for the activity-factor ranges; CDC and NHS on healthy weight and calorie targets; NIH/NIDDK on weight management; and the ISSN position stand on TDEE components (TEF, NEAT). General information only, not medical advice.