Basal Metabolic Rate Converter
Convert basal metabolic rate between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Basal Metabolic Rate Converter
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Formula: BMR (Male) = (10 x weight kg) + (6.25 x height cm) - (5 x age) + 5
Worked example — BMR: 1,618 cal/day | TDEE: 2,507 cal/day | Weight loss: 2,007 cal/day
Formula
BMR (Male) = (10 x weight kg) + (6.25 x height cm) - (5 x age) + 5
The Mifflin-St Jeor equation calculates BMR using weight in kilograms, height in centimeters, and age in years. For females, the constant is -161 instead of +5. TDEE = BMR x Activity Factor, where sedentary = 1.2, light = 1.375, moderate = 1.55, active = 1.725, very active = 1.9. The Harris-Benedict equation uses different coefficients, and the Katch-McArdle formula uses lean body mass: BMR = 370 + (21.6 x lean mass kg).
Worked Examples
Example 1: BMR for a 30-Year-Old Male
Problem:Calculate BMR for a 30-year-old male, 70 kg, 170 cm, with moderate activity level.
Solution:Mifflin-St Jeor: BMR = (10 x 70) + (6.25 x 170) - (5 x 30) + 5 BMR = 700 + 1062.5 - 150 + 5 = 1,618 calories/day TDEE = 1,618 x 1.55 (moderate activity) = 2,507 calories/day BMR per hour: 1,618 / 24 = 67.4 calories/hour Weight loss target: 2,507 - 500 = 2,007 calories/day Weight gain target: 2,507 + 500 = 3,007 calories/day
Result:BMR: 1,618 cal/day | TDEE: 2,507 cal/day | Weight loss: 2,007 cal/day
Example 2: BMR for a 45-Year-Old Female
Problem:Calculate BMR for a 45-year-old female, 60 kg, 165 cm, with light activity.
Solution:Mifflin-St Jeor: BMR = (10 x 60) + (6.25 x 165) - (5 x 45) - 161 BMR = 600 + 1031.25 - 225 - 161 = 1,245 calories/day TDEE = 1,245 x 1.375 (light activity) = 1,712 calories/day Weight loss target: 1,712 - 500 = 1,212 calories/day This is very close to BMR, so a smaller deficit of 300 cal might be safer.
Result:BMR: 1,245 cal/day | TDEE: 1,712 cal/day | Safe deficit: ~1,412 cal/day
Frequently Asked Questions
What is Basal Metabolic Rate and how does it differ from TDEE?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to maintain basic life-sustaining functions such as breathing, circulation, cell production, nutrient processing, and temperature regulation. BMR accounts for approximately 60-75% of total daily energy expenditure. Total Daily Energy Expenditure (TDEE) includes BMR plus calories burned through physical activity (15-30% of total), the thermic effect of food (approximately 10% of calories consumed for digestion), and non-exercise activity thermogenesis (NEAT) like fidgeting and walking. Understanding the difference between BMR and TDEE is crucial for setting accurate calorie targets for weight management.
Which BMR formula is the most accurate?
The Mifflin-St Jeor equation is widely considered the most accurate BMR formula for the general population and is recommended by the Academy of Nutrition and Dietetics. Studies show it predicts BMR within 10% of measured values for approximately 82% of people. The Harris-Benedict equation (revised in 1984) was the standard for decades but tends to overestimate BMR by about 5% in overweight individuals. The Katch-McArdle formula can be more accurate for lean, muscular individuals because it uses lean body mass rather than total weight, directly accounting for the metabolic difference between muscle and fat tissue. For the highest accuracy, indirect calorimetry testing performed in a clinical setting measures actual oxygen consumption to determine BMR.
What factors affect Basal Metabolic Rate?
Several factors significantly influence BMR. Body composition is the primary determinant: muscle tissue burns approximately 6 calories per pound per day at rest compared to 2 calories per pound for fat tissue, which is why muscular individuals have higher BMRs. Age causes BMR to decline by roughly 1-2% per decade after age 20, primarily due to muscle loss. Men typically have 5-10% higher BMR than women of the same weight due to greater muscle mass. Genetics account for approximately 40% of BMR variation between individuals. Hormones, particularly thyroid hormones, significantly regulate metabolic rate. Environmental temperature, caffeine intake, pregnancy, illness, and certain medications can also temporarily alter BMR.
How do you convert a BMR expressed in calories into kilojoules?
Dietary calories are really kilocalories, and one kilocalorie equals exactly 4.184 kilojoules, so multiply the daily figure by 4.184. A BMR of 1,618 kcal per day becomes 1,618 x 4.184 = 6,770 kJ per day. The kilojoule is the SI energy unit used on food labels in Australia, New Zealand and much of Europe, so this conversion matters when you read a nutrition panel abroad or compare an energy target against a label printed only in kJ.
What is the difference between basal metabolic rate and resting metabolic rate?
BMR is measured under strict laboratory conditions: after an overnight fast, following at least eight hours of sleep, lying still in a thermoneutral room with no prior physical activity. Resting metabolic rate (RMR) is measured under looser conditions, so it typically comes out about 5-10% higher because digestion and residual muscle tone are still contributing. Predictive equations such as Mifflin-St Jeor were validated against measured resting values, which is why the two terms are often used interchangeably in calorie planning.
How does the Katch-McArdle formula use lean body mass?
Katch-McArdle ignores total weight and works from fat-free mass with BMR = 370 + (21.6 x lean mass in kg). Lean mass is weight multiplied by (1 - body fat fraction). For a 70 kg person carrying 18% body fat, lean mass is 70 x 0.82 = 57.4 kg, giving 370 + (21.6 x 57.4) = 1,610 kcal per day. Because it prices metabolic tissue directly, it suits lean or heavily muscled people whose weight-based estimates are distorted, but it is only as good as the body fat measurement feeding it.
Why does the activity multiplier matter more than which BMR equation you pick?
The three equations on this page usually land within about 5% of one another for a typical adult, a swing of roughly 80 calories on a 1,600 kcal BMR. The activity factor ranges from 1.2 for sedentary to 1.9 for athletes, a spread of 0.7 x BMR, which on a 1,600 kcal BMR is 1,120 calories per day on the same person. Choosing an honest multiplier, and correcting it against real weight change over two to four weeks, therefore governs the accuracy of your TDEE far more than formula selection.
How do you express a daily BMR as calories per hour or per minute?
Divide the daily figure by 24 for an hourly rate and by 1,440 for a per-minute rate, since a day contains 1,440 minutes. A BMR of 1,618 kcal per day is 1,618 / 24 = 67.4 kcal per hour and 1,618 / 1,440 = 1.12 kcal per minute. The per-minute figure is useful for interpreting fitness tracker readouts, because a device reporting energy burned during an activity is measuring total expenditure, part of which is the basal rate you would have burned lying still anyway.
When is indirect calorimetry worth using instead of a predictive equation?
Indirect calorimetry measures the oxygen you consume and the carbon dioxide you produce, then derives energy expenditure from those gas volumes; the ratio between them, the respiratory quotient, also indicates whether you are burning mostly carbohydrate or mostly fat. Because it measures rather than predicts, it is preferred when an equation is likely to be unreliable: very high or very low body mass index, substantial muscularity, thyroid disorders, or a plateau that persists despite an apparently correct calorie target. It requires a clinic or sports lab and a fasted, rested subject.
What is adaptive thermogenesis and how does prolonged dieting affect BMR?
Adaptive thermogenesis is the drop in energy expenditure that follows sustained weight loss beyond what the smaller body size alone predicts. Part of the fall is mechanical, since a lighter body has less tissue to maintain and every equation here scales with weight, so BMR should be recalculated as you lose. The rest reflects hormonal changes, including reduced thyroid and leptin signalling, plus a quiet reduction in spontaneous movement. Practically, it means a deficit set months ago gradually stops being a deficit, and targets need periodic revision.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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