Compare your Basal Metabolic Rate across multiple scientific formulas
This calculator is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain essential life functions such as breathing, circulation, cell production, and temperature regulation. BMR typically accounts for 60-75% of total daily energy expenditure, making it the single largest component of your calorie burn. Several scientific formulas have been developed over the past century to estimate BMR from basic body measurements. The three most widely used are the Mifflin-St Jeor equation (1990), the Harris-Benedict equation (originally 1919, revised by Roza and Shizgal in 1984), and the Katch-McArdle formula (1996). Each was developed using different study populations and methodologies, which means they can produce somewhat different results for the same individual. This calculator allows you to compare all three formulas side by side, giving you a more complete picture of your likely BMR range. Research published in the Journal of the American Dietetic Association found that the Mifflin-St Jeor equation is the most reliable for estimating BMR in most healthy adults, but if you know your body fat percentage, the Katch-McArdle formula may provide a more personalised estimate as it accounts for lean body mass. The calculator also shows your Total Daily Energy Expenditure (TDEE) at different activity levels, helping you understand your calorie needs for weight maintenance, loss, or gain.
To compare your BMR across multiple formulas: 1. Enter your weight in kilograms. 2. Enter your height in centimetres. 3. Enter your age in years. 4. Select your sex. The Mifflin-St Jeor and Harris-Benedict formulas use different coefficients for males and females, reflecting physiological differences in body composition. 5. Optionally enter your body fat percentage. If provided, the calculator will also compute your BMR using the Katch-McArdle formula, which uses lean body mass rather than total weight. You can estimate your body fat using our Body Fat Calculator. 6. Review your results. The calculator displays your BMR from each formula, an average, and your TDEE at five activity levels from sedentary to very active. Use the chart to visualise how the formulas compare.
This calculator uses three established BMR formulas: **Mifflin-St Jeor (1990) -- generally considered most accurate for most adults:** Male: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5 Female: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161 **Harris-Benedict (revised 1984):** Male: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age) Female: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age) **Katch-McArdle (requires body fat %):** BMR = 370 + (21.6 x lean body mass in kg) Where lean body mass = weight x (1 - body fat percentage / 100) **TDEE Activity Multipliers:** - Sedentary (little/no exercise): BMR x 1.2 - Lightly active (exercise 1-3 days/week): BMR x 1.375 - Moderately active (exercise 3-5 days/week): BMR x 1.55 - Active (exercise 6-7 days/week): BMR x 1.725 - Very active (hard exercise daily or physical job): BMR x 1.9
Important considerations when using BMR estimates: **Accuracy limitations:** All BMR formulas are population-based estimates. Individual BMR can vary by 10-15% from predicted values due to genetics, hormonal status, body composition beyond simple body fat percentage, and metabolic adaptation. For clinical-grade measurement, indirect calorimetry provides the most accurate BMR assessment. **Metabolic adaptation:** If you have been dieting or restricting calories for an extended period, your actual BMR may be lower than predicted (a phenomenon called adaptive thermogenesis). Conversely, overfeeding can temporarily increase BMR. **Which formula to trust:** For most people, the Mifflin-St Jeor equation provides the most reliable estimate. If you are very lean (under 15% body fat for men, under 22% for women) or carry significantly above-average muscle mass, the Katch-McArdle formula is likely more accurate, provided your body fat percentage input is reliable. **Using TDEE for diet planning:** To lose approximately 0.5kg per week, aim for a daily deficit of about 500 kcal below your TDEE. To gain weight, add 300-500 kcal above your TDEE. The NHS recommends that men consume approximately 2,500 kcal and women approximately 2,000 kcal per day as a general guideline.