BMR Calculator (Basal Metabolic Rate)
Basal metabolic rate (BMR) is the minimum amount of energy your body burns at complete rest just to keep you alive: breathing, circulating blood, repairing cells and regulating temperature.
- Based on standard published formulas
- Instant, easy-to-read estimates
- Private: nothing leaves your device
BMR Calculator (Basal Metabolic Rate)
Enter your numbers and press Calculate
The two formulas: Mifflin-St Jeor and Harris-Benedict
Both equations estimate BMR from weight (kg), height (cm), age (years) and sex.
Mifflin-St Jeor (1990):
- Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
- Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
Revised Harris-Benedict (Roza & Shizgal, 1984):
- Men: BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
- Women: BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age
Worked example. A 41-year-old man from Chicago weighs 198 lb (89.8 kg) and stands 5 ft 11 in (180 cm):
1. Mifflin-St Jeor: 10 × 89.8 + 6.25 × 180 − 5 × 41 + 5 = 898 + 1,125 − 205 + 5 = 1,823 kcal/day. 2. Harris-Benedict: 88.362 + 13.397 × 89.8 + 4.799 × 180 − 5.677 × 41 = 88.362 + 1,203.05 + 863.82 − 232.76 = 1,922.5 ≈ 1,922 kcal/day.
The 99-kcal gap (about 5%) is expected, since each equation was fitted to a different study population. Results are rounded to the nearest whole calorie because the real-world accuracy of any BMR formula is roughly ±10%. If you only know pounds and inches, convert first: 1 lb = 0.4536 kg and 1 in = 2.54 cm.
Examples: BMR for three common US profiles
The table compares what each formula returns for three representative profiles:
| Profile | Weight | Height | Age | Mifflin-St Jeor | Harris-Benedict |
|---|---|---|---|---|---|
| Man, office worker | 198 lb (89.8 kg) | 5 ft 11 in (180 cm) | 41 | 1,823 kcal | 1,922 kcal |
| Woman, recreational runner | 150 lb (68 kg) | 5 ft 5 in (165 cm) | 30 | 1,400 kcal | 1,458 kcal |
| Man, retired | 181 lb (82 kg) | 5 ft 9 in (175 cm) | 60 | 1,619 kcal | 1,686 kcal |
Two patterns stand out. First, Harris-Benedict consistently lands higher (58-99 kcal in these cases) because it was calibrated on early- and mid-20th-century study groups with more average lean mass than today's population. Second, age matters a lot: the 60-year-old man weighs less than the 41-year-old but also loses BMR through the age term in both equations. Keep in mind these are resting figures only; a typical American with a desk job and light daily movement burns roughly 1.4 to 1.6 times their BMR over a full day.
How to use this calculator step by step
1. Weight (kg): enter your current weight in kilograms, ideally measured in the morning before breakfast. Decimals are fine (for example, 89.8). If you think in pounds, divide by 2.2046. 2. Height (cm): enter your height in centimeters without shoes. From feet and inches: multiply total inches by 2.54. 3. Age (years): your current age, from 15 to 90 (the formulas were validated on adults). 4. Sex: check the box if you are male; leave it unchecked if you are female. The equations use biological sex because average lean mass differs between sexes. 5. Hit calculate to get two figures in kcal/day: Mifflin-St Jeor and revised Harris-Benedict.
Reading the result: your BMR is not a calorie target; it is what your body burns at total rest. To estimate full daily expenditure, multiply by an activity factor (1.2 sedentary, 1.55 moderate exercise, 1.9 heavy physical work) or use our TDEE calculator linked below. When the two formulas disagree, treat Mifflin-St Jeor as the primary reference.
Why the formulas differ and which one to trust
The Harris-Benedict equation dates back to 1919, built from indirect calorimetry measurements on 239 people living in the early 20th century. In 1984 Roza and Shizgal recalibrated it with additional data (the version this calculator uses), but its population base remains old: subjects who were, on average, leaner and more muscular than Americans today. Mifflin-St Jeor was published in 1990 using 498 US adults, including people with overweight and obesity, which makes it far more representative of the modern population.
That is why Harris-Benedict tends to overestimate BMR by roughly 5%. The systematic review by Frankenfield and colleagues (2005), adopted by the Academy of Nutrition and Dietetics, concluded that Mifflin-St Jeor is the most reliable equation for adults: it landed within ±10% of calorimetry-measured values more often than any competitor.
Practical rule: use Mifflin-St Jeor as your headline number and treat Harris-Benedict as a plausible upper bound. Neither equation sees body composition, so if you carry a lot of muscle (or very little), a lean-mass formula such as Katch-McArdle may fit better.
This page is for educational purposes only and is not medical or nutritional advice. Talk to a physician or registered dietitian before changing your diet.
About this calculator
It typically accounts for 60-70% of the calories you burn in a day. This calculator estimates it with the two most widely cited equations: Mifflin-St Jeor (1990) and the revised Harris-Benedict (1984). For example, a 41-year-old man weighing 198 lb (89.8 kg) at 5 ft 11 in (180 cm) has a BMR of about 1,823 kcal/day under Mifflin-St Jeor. Enter your weight, height, age and sex to get both results side by side. This tool is for education only; talk to a registered dietitian before changing your diet.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is only the energy you burn at complete rest. Total daily energy expenditure (TDEE) adds physical activity, digestion and everyday movement; it is estimated by multiplying BMR by a factor between 1.2 (sedentary) and 1.9 (very active). A 1,500 kcal BMR can translate into a real-world burn of 1,800 to 2,850 kcal depending on your lifestyle.
Which formula is more accurate, Mifflin-St Jeor or Harris-Benedict?
For most adults today, Mifflin-St Jeor. The Frankenfield (2005) review rated it the most reliable against indirect calorimetry, while Harris-Benedict tends to overestimate by around 5% because it was calibrated on populations from a century ago. We show both so you can see the plausible range of your metabolism.
Is it safe to eat below my BMR?
As a general rule, it is not a sensible long-term target. Weight-loss deficits are set against total expenditure (TDEE), not BMR, and very aggressive deficits are associated with muscle loss, fatigue and micronutrient shortfalls. Any weight-loss plan should be supervised by a healthcare professional; this tool does not replace that advice.
Why does BMR drop with age, and can you slow the decline?
Mostly because of the gradual loss of muscle mass (sarcopenia): muscle burns more energy at rest than fat does. You can see it in the negative age term of both formulas, roughly 25-50 fewer kcal per 5 years. Regular strength training and adequate protein intake help preserve lean mass and, with it, part of that resting burn.