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BMR Formula: Equations, Worked Examples and TDEE

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The most widely recommended BMR formula is the Mifflin-St Jeor equation: for men, BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5, and for women the same expression with −161 in place of +5. The result is an estimate of the calories your body uses at rest in a day. It is a starting point for planning, not a measurement and not a daily eating target.

Below we cover the equations, a worked example in both metric and US units, how BMR differs from TDEE, and where the formulas break down. We lay out the numbers so you can check the arithmetic yourself.

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TL;DR

  • Mifflin-St Jeor (men: 10W + 6.25H − 5A + 5; women: 10W + 6.25H − 5A − 161, with W in kg, H in cm, A in years) is the default choice for most adults.
  • BMR is not your calorie allowance. Multiply it by an activity factor between 1.2 and 1.9 to estimate TDEE.
  • Expect an error of roughly 10% for many people, and larger uncertainty for athletes and people with high lean mass.
  • Convert pounds and inches first: 1 lb = 0.45359237 kg and 1 in = 2.54 cm.

Table of Contents

The BMR formulas in common use

Three equations appear most often in search results and calculators. They give different numbers for the same person, because they were fitted to different groups of people in different decades.

Equation Men Women
Mifflin-St Jeor 10W + 6.25H − 5A + 5 10W + 6.25H − 5A − 161
Revised Harris-Benedict 88.362 + 13.397W + 4.799H − 5.677A 447.593 + 9.247W + 3.098H − 4.330A
Katch-McArdle Based on lean body mass, same for both sexes Same

In every case, W is weight in kilograms, H is height in centimeters and A is age in years. The Mifflin-St Jeor version for both sexes is published by Healthline, and the revised Harris-Benedict male equation is given by the Cleveland Clinic. The female revised Harris-Benedict coefficients are the standard published values; the original 1919 constants (66.5 and 655.1) still circulate on some pages, which is one reason two calculators can disagree.

Why Mifflin-St Jeor is the usual default

A systematic review of predictive equations in the Journal of the American Dietetic Association compared the four equations most used in clinical practice (Harris-Benedict, Mifflin-St Jeor, Owen and the WHO/FAO/UNU equations). It found Mifflin-St Jeor was the most likely to land within 10% of measured resting metabolic rate in both nonobese and obese adults. That is the main reason it is recommended over the older Harris-Benedict revisions.

“Most accurate” is relative, though. Within 10% means a person whose true rate is 1,600 kcal/day could be estimated anywhere from about 1,440 to 1,760 kcal/day and still count as a hit. And some people fall outside that band.

Katch-McArdle and lean mass

Katch-McArdle does not use age, sex or height directly. It starts from lean body mass, so it needs a body fat estimate. A meta-analysis of resting metabolic rate equations in athletes found that generic population equations tend to be less reliable for athletes, and it identified the Ten-Haaf equation as the most precise of the nine that met its criteria. If you are very muscular, a lean-mass formula is a reasonable cross-check. Our body fat percentage calculator can give you the body fat input that such a formula needs, with the usual caveat that tape-measure estimates are rough.

How to calculate BMR step by step

  1. Convert to metric. If you use pounds and inches, multiply pounds by 0.45359237 for kilograms and inches by 2.54 for centimeters. The unit converter does this without rounding errors creeping in.
  2. Pick the equation. Mifflin-St Jeor unless you have a reason not to.
  3. Multiply each term. Weight by 10, height by 6.25, age by 5.
  4. Add and subtract. Add weight and height terms, subtract the age term, then add 5 (men) or subtract 161 (women).
  5. Round at the end. Rounding intermediate terms adds avoidable error, though the effect is small compared with the formula’s own uncertainty.

BMR examples with real numbers

The people below are hypothetical, chosen to make the arithmetic easy to follow. They are not data from a study.

Example 1: a woman in metric units

Age 35, 70 kg, 165 cm, Mifflin-St Jeor:

  • 10 × 70 = 700
  • 6.25 × 165 = 1,031.25
  • 5 × 35 = 175
  • BMR = 700 + 1,031.25 − 175 − 161 = 1,395.25, about 1,395 kcal/day

Example 2: a man in metric units

Age 30, 80 kg, 180 cm:

  • 10 × 80 = 800
  • 6.25 × 180 = 1,125
  • 5 × 30 = 150
  • BMR = 800 + 1,125 − 150 + 5 = 1,780 kcal/day

Example 3: the same man with Harris-Benedict

  • 13.397 × 80 = 1,071.76
  • 4.799 × 180 = 863.82
  • 5.677 × 30 = 170.31
  • BMR = 88.362 + 1,071.76 + 863.82 − 170.31 = 1,853.63, about 1,854 kcal/day

The two equations differ by about 74 kcal/day for this person (roughly 4%). That gap is small next to the 10% error band, which is a useful reminder that choosing between equations matters less than treating the output as a range.

Example 4: US units

A 154 lb, 65 in woman, aged 35. First convert: 154 × 0.45359237 = 69.85 kg, and 65 × 2.54 = 165.1 cm.

  • 10 × 69.85 = 698.5
  • 6.25 × 165.1 = 1,031.875
  • 5 × 35 = 175
  • BMR = 698.5 + 1,031.875 − 175 − 161 = 1,394.4, about 1,394 kcal/day

Nearly identical to Example 1, as expected, since the inputs are nearly the same person.

BMR vs TDEE: the step most people skip

BMR covers the energy your body uses at rest. Total daily energy expenditure (TDEE) adds the cost of moving, exercising and digesting food. The usual shortcut, described by Healthline, multiplies BMR by an activity factor:

Activity level Factor Woman, BMR 1,395 Man, BMR 1,780
Sedentary 1.2 1,674 2,136
Lightly active 1.375 1,918 2,448
Moderately active 1.55 2,162 2,759
Very active 1.725 2,406 3,071
Extra active 1.9 2,651 3,382

The last two columns are our arithmetic on the hypothetical examples above, rounded to the nearest calorie. The factors themselves are rules of thumb, and most people overestimate how active they are. If you are between two levels, the lower one is the safer assumption for a first estimate.

A common mistake is reading the BMR figure as the amount to eat. Healthline notes that eating only at your BMR is generally not recommended, since it represents energy for basic functions only. If your goal involves gaining or losing weight, TDEE is the number to adjust from, and a doctor or registered dietitian is the right person to set a target if you have a medical condition, are pregnant, or plan a large change in intake. We walk through that adjustment in our calorie deficit formula guide, and the calorie calculator article explains what to look for in an estimate.

Where activity data fits

Watches and bands estimate activity-related burn using heart rate and movement, and that estimate can replace the crude activity multiplier. If you are curious how those devices read intensity, this piece on how wearables measure exercise intensity is a reasonable place to start. Treat device calorie figures with the same caution as the formulas: both are estimates.

BMR vs RMR: a terminology problem

Strictly, BMR is measured in a lab after sleep, 12 to 14 hours after eating, in a thermally neutral room. Most online calculators, and the equations above, actually predict resting metabolic rate (RMR), which includes slightly more activity. According to the Cleveland Clinic, the two terms are used interchangeably in consumer tools, and RMR runs about 10% higher than true BMR. For planning purposes the distinction is smaller than the formula error, but it explains why a lab result and a calculator may not match.

BMR and RMR measurement conditions compared

What counts as a normal BMR

There is no single normal value. The Cleveland Clinic cites averages of roughly 1,696 kcal/day for men and 1,410 kcal/day for women, and these are general-awareness estimates, not clinical standards. The same page notes that metabolic rate tends to fall by 1% to 2% per decade after the second decade of life. Muscle mass, age and sex all move the number.

So a woman at 1,395 kcal/day (Example 1) is near the quoted average, and a man at 1,780 kcal/day (Example 2) is a little above his. Neither result says anything about health. If you are asking whether your own value is “good” for your age, the honest answer is that a calculated figure cannot tell you that.

What counts as a normal BMR — overview diagram

Limits of any BMR formula

We built this section from the research rather than opinion, and the points are consistent across sources:

  • Error of around 10%. The systematic review found that even the best-performing equation leaves a meaningful share of people outside the 10% band.
  • Athletes and high lean mass. Standard equations tend to underperform here, per the athlete meta-analysis.
  • Hidden variables. The equations use only a few inputs. They do not reflect thyroid function, hormone levels or metabolic adaptation after dieting, as the Cleveland Clinic points out.
  • Gold standard. Indirect calorimetry measures resting metabolic rate directly, and is used when precise values are medically necessary. Ask a clinician if you think you need it.

A practical response is to use the formula as a hypothesis. Eat at your estimated TDEE for two to three weeks while tracking weight, then adjust based on what actually happens. That is data about you, which beats any equation.

Doing the arithmetic in your browser

The calculation above needs only multiplication, so a spreadsheet or phone calculator works. If you want help with the surrounding steps, GizmoBench has browser-based tools that run locally, with no account and no installation. The unit converter handles pounds, kilograms, inches and centimeters, and the percentage calculator is useful for working out what a 10% error band means in calories. More everyday tools are listed on our everyday tools page.

FAQ

Which BMR formula is the most accurate?

For the general adult population, Mifflin-St Jeor has the best track record in the published comparison of common equations. For athletes and very muscular people, a lean-mass-based or athlete-specific equation may do better. No formula is exact for every individual.

How do I calculate BMR from pounds and inches?

Convert first: multiply pounds by 0.45359237 to get kilograms and inches by 2.54 to get centimeters. Then apply the equation as usual. Example 4 above shows the full calculation for a 154 lb, 65 in woman.

Is BMR the same as TDEE?

No. BMR is resting energy use, while TDEE includes daily movement and exercise. You estimate TDEE by multiplying BMR by an activity factor from 1.2 to 1.9.

Should I eat at my BMR to lose weight?

Generally no. BMR reflects only basic functioning, and eating at that level may fall below a safe intake. If you want to lose weight, start from your estimated TDEE and talk to a doctor or registered dietitian, especially if you have a medical condition.

Sources