TDEE vs BMR: Formulas and the Difference Explained

What is the difference between BMR and TDEE?

BMR is what your body burns if you do nothing at all, and TDEE is what you burn in a real day. BMR pays for breathing, circulation, temperature control and organ function, measured at complete rest. TDEE is that plus every other use of energy.

TDEE has three parts beyond BMR: exercise, everyday movement such as walking and fidgeting, and the thermic effect of food, the energy used to digest what you eat, usually put at roughly 10% of intake. BMR is the largest single part for most people. You may also see RMR (resting metabolic rate), which is measured under less strict conditions than BMR and comes out slightly higher, but the two are often used interchangeably in calculators.

What is the Mifflin-St Jeor equation?

The Mifflin-St Jeor equation predicts BMR from weight, height, age and sex. It was published in 1990 from measurements of 498 healthy adults aged 19 to 78, about half of normal weight and half with obesity, and it is the default in our BMR calculator.

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

How do you calculate BMR with Mifflin-St Jeor?

Convert to metric, multiply each measurement by its coefficient, then add the sex-specific constant. Take a 40-year-old man who is 5 feet 10 inches (177.8 cm) and 200 pounds (90.7 kg): 907.2 + 1,111.25 − 200 + 5 = 1,823 calories a day.

For a 35-year-old woman who is 5 feet 5 inches (165.1 cm) and 160 pounds (72.6 kg): 725.7 + 1,031.9 − 175 − 161 = 1,422 calories a day. Both results match what our calculator returns for those inputs.

What is the Harris-Benedict formula?

The Harris-Benedict formula is an older BMR equation that dates to 1918 and was revised in 1984 by Roza and Shizgal. The revised version is the one most calculators use, including ours.

With the same two people, revised Harris-Benedict gives 1,930 calories for the man (107 more than Mifflin-St Jeor) and 1,479 for the woman (57 more). The Mifflin paper reported that the original Harris-Benedict equations overestimated measured resting energy by about 5%, and a 2005 systematic review in the Journal of the American Dietetic Association found Mifflin-St Jeor predicted resting metabolic rate within 10% of measured in more people than the other equations it compared.

• Men: BMR = 13.397 × weight (kg) + 4.799 × height (cm) − 5.677 × age + 88.362
• Women: BMR = 9.247 × weight (kg) + 3.098 × height (cm) − 4.330 × age + 447.593

When should you use Katch-McArdle instead?

Use Katch-McArdle if you know your body fat percentage fairly accurately, especially if you are lean and muscular. It works from lean body mass rather than total weight: BMR = 370 + 21.6 × lean body mass (kg), so age and sex do not appear in it.

For the 200-pound man at 25% body fat, lean mass is 68.0 kg, which gives a BMR of 1,840 calories and a TDEE of 2,530 with light exercise. The answer is only as good as the body fat figure; see how to measure body fat for how far those measurements can be trusted. Our BMR calculator offers all three formulas, and our TDEE calculator offers Mifflin-St Jeor and Katch-McArdle.

What is the TDEE formula and which activity multiplier should you use?

The TDEE formula is TDEE = BMR × activity multiplier. Pick the row that matches a typical week, not your best week. Our TDEE calculator uses the multipliers below; the table applies them to the two examples, using their Mifflin-St Jeor BMRs of 1,422 and 1,823 calories.

In these labels, exercise means 15 to 30 minutes with an elevated heart rate, intense exercise means 45 to 120 minutes, and very intense exercise means 2 hours or more. The multipliers are conventions rather than measured values for any one person, and the moderate level of 1.465 is an in-between step some calculators add to the older five-level scale.

How accurate are BMR and TDEE estimates?

They are good starting points, not measurements, and individuals can sit well above or below the prediction. Equations describe averages across a group, and the 2005 review noted real errors when they are applied to individuals, and that older adults and US ethnic minorities were underrepresented in the validation studies.

Choosing an activity level adds more uncertainty, since the gap between activity levels can be a few hundred calories. For the man above, moving from active to very active changes TDEE by 319 calories a day.

The practical check is your weight trend. Eat at your estimated TDEE for two to four weeks. If your weight holds steady, the estimate is about right for you. If it drifts up or down, adjust your number by 100 to 200 calories and repeat.

Which number should you use to plan your diet?

Use TDEE. It is the estimate of what you actually burn, so weight goals are set relative to it: eat below TDEE to lose, at TDEE to maintain, above TDEE to gain. BMR is useful mainly as the input to TDEE and for comparing formulas.

A deficit of about 500 calories below TDEE leads to about 1 pound of loss a week at first, which puts the example man at 2,007 calories. Our guide on how many calories to eat to lose weight covers safe rates and minimum intakes, and how to calculate macros shows how to split the total. If you are pregnant, breastfeeding, have kidney disease or have a history of an eating disorder, set targets with a clinician.