BMR vs TDEE
BMR is what you burn lying still. TDEE is BMR plus your day. Deficits are set from TDEE.
Basal metabolic rate (BMR) is the energy your body uses at complete rest, awake, fasted, in a warm room: breathing, circulation, cell repair, keeping organs running. Total daily energy expenditure (TDEE) is BMR plus the cost of everything you do, from digesting breakfast to walking to the car to a workout. BMR is the floor; TDEE is the whole building.
For a 35-year-old woman at 5 ft 5 in and 160 lb, BMR is 1,422 kcal and a lightly active TDEE is 1,955 kcal, a 533 kcal difference. For a moderately active 176 lb man the gap is 961 kcal. Most online confusion about calories comes from mixing the two up.
Side by side
| BMR | TDEE | |
|---|---|---|
| What it measures | Energy at complete rest | Energy for the whole day |
| How it is estimated | Equation from sex, age, height, weight (or lean mass) | BMR × activity factor (1.2 to 1.9) |
| Share of the total | Usually 60 to 75% | 100% |
| Changes when | Weight, age or lean mass change | Those, plus any change in job, steps or training |
| Use it for | Understanding your baseline; a sanity check on very low targets | Setting maintenance, deficit and surplus calories |
Do you calculate a calorie deficit from BMR or TDEE?
From TDEE. A deficit is calories eaten below calories burned, and calories burned is TDEE. Subtracting 500 from BMR instead gives a target that is 500 kcal below resting needs plus the entire activity cost on top, often a deficit of 1,000 kcal or more without meaning to. For the woman above, TDEE − 500 is 1,455 kcal; BMR − 500 would be 922 kcal, below this site's floor.
Can you eat below your BMR?
Physiologically, yes, and people on supervised diets do. Eating below BMR does not "shut down" metabolism; the body draws the difference from stored fat, which is the point of a deficit. The practical problem is nutrition: below about 1,200 kcal for women and 1,500 for men it is hard to cover protein and micronutrients from food, which is why the weight-loss calculator applies those floors rather than a BMR floor.
RMR, REE and BMR
You will see resting metabolic rate (RMR) and resting energy expenditure (REE) used interchangeably with BMR. Strictly, BMR is measured under tighter conditions (overnight fast, after a full night's sleep, in the lab) and RMR under looser ones, so RMR runs a few percent higher. The Mifflin-St Jeor equation was fitted to resting measurements, so what calculators call BMR is technically RMR. The difference is well inside the equation's error and changes nothing about how you use the number.
Questions
Is TDEE or BMR more important for weight loss?
TDEE, because it is the number your intake is compared with. BMR is useful as context: a target that falls below it is a sign the deficit is aggressive, even if it is not dangerous by itself.
How do I calculate TDEE from BMR?
Multiply BMR by 1.2 for sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active or 1.9 extra active. The calculator on this site does both steps and shows them.
Why is my BMR higher than my friend's but my TDEE lower?
Because TDEE depends on the day, not just the body. A larger person with a desk job and no training can have a higher BMR and a lower TDEE than a smaller person with a physical job. The activity factor is where the difference comes in.
By Alton Vieira · Updated . Estimates for healthy adults; not medical advice. How every number is calculated.
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990.
- 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.