BMR vs TDEE: What the Numbers Mean

What BMR is

BMR stands for basal metabolic rate. It is the energy your body uses in a day doing nothing but staying alive: breathing, pumping blood, keeping warm, repairing cells, running the brain. If you stayed in bed for 24 hours you would still burn this much. Whenever the day's total is less than twice the BMR, which the activity bands below show is true for a desk worker, it is the largest share of the calories you use.

A lab measures it directly. A calculator estimates it from four inputs: sex, age, height and weight. Bigger and younger bodies burn more. Men burn somewhat more than women of the same size and age, which the formula below handles with a different constant.

What TDEE adds

TDEE is total daily energy expenditure: BMR plus everything you do on top of staying alive. Walking, typing, cooking, training, even digesting food. Nobody can add all of that up, so calculators multiply the BMR by an activity factor that stands for a typical week.

TDEE is the number that matters for your weight. Eat about this much and the scale stays put, which is why it is also called maintenance calories. Eat less and you lose, eat more and you gain. BMR on its own is never an eating target. It describes a body that does nothing, and nobody does nothing.

The Mifflin-St Jeor formula, worked through

The calorie calculator uses the equation that Mifflin, St Jeor and colleagues published in 1990, derived from measurements of 498 healthy adults, 247 women and 251 men. A 2005 systematic review in the Journal of the American Dietetic Association compared the common equations and found that this one predicted the measured resting rate within 10 percent in more people than any other, in both non-obese and obese adults.

Men: 10 × weight in kg + 6.25 × height in cm − 5 × age in years + 5
Women: 10 × weight in kg + 6.25 × height in cm − 5 × age in years − 161

Take a 30-year-old man, 175 cm tall, 75 kg. Weight: 10 × 75 = 750. Height: 6.25 × 175 = 1,093.75. Age: 5 × 30 = 150. Put together: 750 + 1,093.75 − 150 + 5 = 1,698.75, so about 1,699 kcal a day. A woman with the same age, height and weight gets 166 kcal less, because the constant is −161 instead of +5: 1,533 kcal.

Now the activity factor. The table shows the man's TDEE at each level the calculator offers.

Activity level	Factor	TDEE (kcal/day)
Sedentary: desk job, little or no exercise	1.2	2,039
Lightly active: light exercise 1 to 3 days a week, or a job with some walking	1.375	2,336
Moderately active: moderate exercise 3 to 5 days a week	1.55	2,633
Very active: hard exercise 6 to 7 days a week, or a physical job	1.725	2,930
Extra active: training twice a day, or hard physical work plus training	1.9	3,228

The gap between the top and the bottom row is almost 1,200 kcal a day, on the same body. No other input moves the result that much, so rate a normal week, not your most ambitious one.

Where the activity factors come from

Nutrition science has a name for the ratio of total energy use to BMR: physical activity level, or PAL. The FAO/WHO/UNU report Human energy requirements defines it as total energy expenditure divided by BMR and groups lifestyles into three bands: sedentary or light activity from 1.40 to 1.69, active or moderately active from 1.70 to 1.99, and vigorous from 2.00 to 2.40. Its example for the sedentary band is a male office worker. It adds that one hour of moderate to vigorous exercise a day can lift a person from an average PAL of 1.55 into the moderately active band, and that values above 2.40 are hard to keep up for long.

The five-step ladder from 1.2 to 1.9 that most calculators use, this one included, spreads finer steps across roughly the same range. Compare the two scales and one thing stands out: the lowest step, 1.2, sits below the FAO band for office workers, which starts at 1.40. So if you have a desk job and no sport, 1.375 is the closer match to that classification, not 1.2.

Using TDEE for a deficit or surplus

Once you have TDEE, the rest is subtraction. Harvard Health Publishing ties a deficit of 500 to 1,000 kcal a day to a loss of about 1 to 2 lb a week, the pace it describes as safe, and the CDC says people who lose weight at that gradual, steady rate are more likely to keep it off. For the moderately active man above: 2,633 − 500 = 2,133 kcal a day for roughly 1 lb a week.

Two guardrails. Harvard advises not going below 1,200 kcal a day for women and 1,500 for men without a health professional involved. And the target is not fixed: as the weight comes down, so does the BMR, so put the new weight into the calculator after a noticeable change and take the deficit from the fresh TDEE.

A surplus works the same way in reverse. Eating 300 kcal above the 2,633 maintenance level is 2,933 kcal a day. From there, the macro calculator splits the calories into protein, carbs and fat. To see where you stand before you start, the BMI calculator places your weight on the standard scale and the ideal weight calculator shows what the common height-based formulas suggest.

Mistakes that throw the number off

Eating at BMR. A BMR of 1,699 is not a diet plan. It leaves out everything you do all day, so the real deficit would be your whole activity, far more than the 500 to 1,000 kcal range above.
Counting exercise twice. The activity factor already contains your training. If you also add the calories a watch shows for a run and eat them back, the run is counted twice.
Picking the row you aspire to. Three planned gym sessions that turn into one real one belong in Lightly active, not Moderately active. On this example the difference is almost 300 kcal a day.
Treating the estimate as exact. The equation is the best of the common ones, but its benchmark in the 2005 review was plus or minus 10 percent. Watch the scale for two or three weeks and adjust by 100 to 200 kcal if it moves the wrong way.

The equation was built on healthy adults. If you are pregnant, ill, or take medication that affects your weight, talk to a doctor or dietitian before you change how much you eat.

Frequently asked questions

Is BMR the same as resting metabolic rate?

For a calculator, yes. The 1990 paper calls its result resting energy expenditure (REE), the 2005 review speaks of resting metabolic rate (RMR), and calculators label the same number BMR. The strict lab definitions differ in how the measurement is taken, but the equation is the same, and the activity factor is a far bigger source of uncertainty than the label.

Should I eat my BMR to lose weight?

No. BMR describes a body that does nothing all day, so eating that little means a deficit equal to your entire activity, which is usually far more than the 500 to 1,000 kcal a day that Harvard Health Publishing links to a safe 1 to 2 lb a week. Work from TDEE instead and subtract from there.

How accurate is a TDEE calculator?

The 2005 review that compared the common equations used a benchmark of plus or minus 10 percent of the measured resting rate, and Mifflin-St Jeor hit that benchmark in more people than the alternatives. On a TDEE of about 2,600 kcal that still leaves a band of roughly 260 kcal either way. Let the scale correct the number over two or three weeks.

Does muscle change my BMR?

Not in this formula. It only sees weight, height, age and sex, so two people with the same numbers get the same BMR no matter how much muscle either carries. If you are unusually lean or unusually muscular, treat the estimate as rougher than usual and let your weight trend over a few weeks correct it.

Why does my TDEE drop after I lose weight?

Every kilogram you lose is a kilogram your body no longer has to feed and carry. Put the new weight into the formula and the BMR falls, and the activity multiplier scales that smaller number. That is one reason weight loss slows over time, and why it pays to recalculate after a noticeable change.

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Written by Tobias Kurth, designer. Updated October 13, 2026.