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BMR Calculator

See your resting calorie burn from two trusted equations, side by side.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Select your sex and enter your age, weight in kilograms, and height in centimeters.
  2. 2.Read your Basal Metabolic Rate from the Mifflin-St Jeor equation, shown as the primary result.
  3. 3.Compare it with the revised Harris-Benedict estimate to see your resting-calorie range.

About BMR Calculator

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep you alive — powering your heart, brain, lungs, kidneys, and the constant work of maintaining body temperature and cell repair. It is the single largest slice of most people's daily energy budget, typically accounting for 60 to 70 percent of the calories you burn in a day, before any movement, digestion, or exercise is added. Because you cannot easily measure it without a metabolic cart in a lab, researchers built prediction equations that estimate BMR from four simple inputs: sex, weight, height, and age. This calculator runs two of the most widely used equations at once so you can see how they compare.

The first is the Mifflin-St Jeor equation, published in 1990. It is the formula most modern dietitians and clinical guidelines reach for, because when it was validated against measured resting metabolic rate it predicted values within about 10 percent for a larger share of people than the older alternatives. Its structure is deliberately simple: 10 × weight in kilograms plus 6.25 × height in centimeters minus 5 × age in years, then add 5 for men or subtract 161 for women. That single sex offset — a swing of 166 calories between an otherwise identical man and woman — reflects average differences in lean body mass.

The second is the Harris-Benedict equation. The original dates to 1919, but this tool uses the 1984 revision by Roza and Shizgal, which re-fit the coefficients to a larger, more representative sample. For men it is 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age; for women, 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age. Notice the larger constant terms and steeper weight coefficient: for a typical adult the revised Harris-Benedict usually returns a slightly higher BMR than Mifflin-St Jeor. Seeing both numbers side by side makes that gap concrete and reminds you that every prediction equation is an estimate built from population averages, not a personal measurement.

Why show two equations instead of one? Because the honest answer to "what is my BMR?" is a range, not a single figure. Individual metabolism is shaped by body composition, thyroid function, genetics, and adaptation to dieting — none of which appear in a height-and-weight formula. Two respected equations disagreeing by 50 to 100 calories is a useful visual cue that you should treat any BMR figure as a starting reference point, then adjust based on real-world results over several weeks.

Unlike a full calorie calculator, this tool intentionally stops at the resting number. It does not multiply by an activity factor or apply a weight-loss or weight-gain goal — that is the job of Total Daily Energy Expenditure. Keeping BMR isolated lets you understand your true baseline first. Everything runs locally in your browser: nothing you type is uploaded or stored. To turn this resting figure into daily calorie targets that include activity and goals, use the calorie calculator; to check where your weight sits relative to height, use the BMI calculator.

Methodology & sources

BMR is estimated with two published prediction equations. Mifflin-St Jeor (1990): BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5 for men, or − 161 for women; it is the equation most current clinical and dietetic guidelines recommend for resting energy prediction. Harris-Benedict, revised version (Roza & Shizgal, 1984): men = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age(years); women = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age(years). The Mifflin-St Jeor result is shown as the primary figure (rounded to the nearest whole calorie) and Harris-Benedict as a comparison. Assumptions: inputs use metric units (kg, cm, years); results assume a healthy adult and do not adjust for pregnancy, athletic body composition, illness, or medications; both equations are population-average estimates, not personal measurements, so real resting metabolism can differ by roughly ±10 percent or more. This tool reports resting BMR only and does not apply activity multipliers or weight goals. This is for general information only and is not medical advice; consult a qualified healthcare professional before making health, diet, or medical decisions.

Frequently asked questions

What is Basal Metabolic Rate (BMR)?
BMR is the number of calories your body burns at complete rest to sustain vital functions like breathing, circulation, and cell repair — typically 60 to 70 percent of daily energy use, before any activity or digestion is added.
Which is more accurate, Mifflin-St Jeor or Harris-Benedict?
Most modern clinical and dietetic guidelines prefer the Mifflin-St Jeor equation (1990), which validated within about 10 percent for more people than the older Harris-Benedict. This tool shows both so you can see the likely range rather than a single number.
Is this BMR estimate medical advice?
No. Both equations are population-average estimates and can differ from your true metabolism by roughly 10 percent or more. This is for general information only — consult a qualified healthcare professional for medical or dietary decisions.

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