BMR Calculator (Mifflin-St Jeor)

Enter your weight, height, age, and biological sex to calculate your Basal Metabolic Rate and estimated daily calorie needs at multiple activity levels.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter your Weight
Input your current body weight in pounds. For accuracy, use a recent measurement.
2
Enter your Height
Specify your height in total inches (e.g., 5 ft 10 in = 70 in).
3
Enter your Age
Input your age in whole years. Age is a significant factor in metabolic rate.
4
Select your Biological Sex
Choose Male or Female. This determines which formula constant is applied.
5
Review your results
The calculator displays six cards: Basal Metabolic Rate, Hourly Calorie Burn, Weekly BMR, Sedentary TDEE, Moderate Activity TDEE, and Active TDEE.

Example Calculation

A 30-year-old male weighing 170 lbs and 5 ft 10 in tall wants to know his BMR and activity-adjusted targets.

Weight

170

Height

Age

Biological Sex

Male

Results

Basal Metabolic Rate

1,737 cal/day, Hourly Calorie Burn: 72.4 cal/hr, Weekly BMR: 12,162 cal, Sedentary TDEE: 2,085 cal/day, Moderate Activity TDEE: 2,693 cal/day, Active TDEE: 2,997 cal/day

Tips

Refine with Activity

Your BMR is just your resting burn. To estimate total daily energy expenditure, multiply your BMR by an activity factor. A sedentary individual might use 1.2, while a very active person could use 1.7-1.9.

Track Over Time

BMR can fluctuate with significant changes in weight, muscle mass, or age. Re-calculate every 3-6 months, or after a weight change of 10+ pounds, to ensure your calorie targets remain accurate.

Consider Muscle Mass

Muscle tissue burns more calories at rest than fat tissue. If you're highly muscular, your actual BMR might be slightly higher than the Mifflin-St Jeor estimate, potentially by 50-100 calories per day, as this formula doesn't directly account for body composition.

Understanding Your Basal Metabolic Rate

Your Basal Metabolic Rate (BMR) represents the minimum number of calories your body needs to perform fundamental life-sustaining functions while at rest. This includes breathing, circulation, nutrient processing, and cell production. Knowing your BMR is a cornerstone for effective weight management, whether you're aiming for loss, maintenance, or gain. For instance, a typical adult BMR can range from 1,200 to over 2,000 calories per day, directly influencing how many calories you can consume without gaining weight.

The Mifflin-St Jeor Formula in Action

The Mifflin-St Jeor equation is a widely accepted formula for estimating Basal Metabolic Rate, recognized for its improved accuracy over older methods. It considers your weight, height, age, and biological sex to provide a personalized estimate of your resting energy expenditure. This calculation is vital because it establishes your body's baseline caloric needs, informing dietary planning by setting the foundational energy requirement before accounting for any physical activity.

The formula used by this BMR calculator (Mifflin-St Jeor) is:

For males: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
For females: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Here, weight is converted from pounds to kilograms (1 lb = 0.453592 kg), and height from inches to centimeters (1 in = 2.54 cm) before applying the formula.

💡 While BMR focuses on true resting metabolism, our Resting Energy Expenditure (REE) Calculator can provide a similar estimate that often includes minor digestive processes, which some find more practical for daily planning.

Calculating a Female's Daily Basal Metabolic Rate

Consider a 35-year-old female, who is 5 feet 6 inches tall and weighs 145 pounds, looking to determine her resting caloric needs.

Convert weight to kilograms: 145 lbs × 0.453592 = 65.77 kg
Convert height to centimeters: 66 inches × 2.54 = 167.64 cm
Apply the female Mifflin-St Jeor formula: BMR = (10 × 65.77) + (6.25 × 167.64) - (5 × 35) - 161 BMR = 657.7 + 1047.75 - 175 - 161 BMR = 1,399.45 calories/day

Therefore, this individual's Basal Metabolic Rate is approximately 1,399 calories per day. This means her body burns roughly 1,399 calories simply to maintain its basic functions over a 24-hour period.

💡 Beyond your BMR, understanding the calories burned during digestion is also important. Our Thermic Effect of Food (TEF) Calculator can help you estimate this additional energy expenditure.

Dietary Context

For individuals focused on weight management, BMR provides the baseline for calorie targets. A common recommendation for sustainable weight loss is to create a daily caloric deficit of 500-750 calories below your Total Daily Energy Expenditure (TDEE), which is BMR plus activity. This typically leads to a weight loss of 1-1.5 pounds per week. For instance, if your TDEE is 2,000 calories, a target of 1,250-1,500 calories per day would align with these guidelines. Athletes or those with significant muscle mass might find their BMR is on the higher end, requiring more calories to maintain their physique and performance, often needing 2,500-3,500 calories or more daily depending on training intensity. The Academy of Nutrition and Dietetics often recommends that calorie intake should not drop below 1,200 calories per day for women and 1,500 for men to ensure adequate nutrient intake.

What bmr calculator (mifflin-st jeor) results look like in practice

Professionals across nutrition and fitness utilize BMR results in various contexts, each with specific benchmarks. In clinical dietetics, a BMR below 1,000 calories/day for an average adult female or 1,200 calories/day for an average adult male might signal a severely restricted diet or a metabolic issue requiring further investigation, as these levels are often insufficient for basic bodily functions. For personal trainers, BMR is the starting point for calculating a client's Total Daily Energy Expenditure (TDEE); they typically multiply BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active) to set realistic calorie goals for muscle gain or fat loss. In sports nutrition, an athlete's BMR is crucial for preventing underfueling, where their BMR combined with high training volumes might mean a daily intake of 3,000-5,000 calories is necessary to maintain performance and recovery. For general wellness coaching, a BMR that appears significantly lower than expected for an individual's physical profile might prompt discussions around metabolism, body composition, and lifestyle factors.

Frequently Asked Questions

What is a good BMR for an adult?

A 'good' BMR varies significantly by individual, influenced by age, gender, height, and weight. For example, a 30-year-old male, 5'10" and 180 lbs, might have a BMR around 1,800 calories/day, while a 50-year-old female, 5'4" and 130 lbs, might have a BMR closer to 1,250 calories/day. These numbers represent the minimum calories needed to sustain basic bodily functions.

How accurate is the Mifflin-St Jeor equation?

The Mifflin-St Jeor equation is considered one of the most accurate predictive BMR formulas for a general adult population, often within 10% of actual measured BMR for most individuals. It's generally preferred over older formulas like Harris-Benedict for its slightly better precision.

Does BMR decrease with age?

Yes, BMR typically decreases with age due to a natural decline in muscle mass and metabolic activity. After age 20, BMR can decrease by approximately 1-2% per decade, meaning a 50-year-old might have a BMR 3-6% lower than their 20-year-old self, assuming similar body composition.

Can I increase my BMR?

The most effective way to slightly increase your BMR is by building muscle mass through strength training. Muscle tissue is metabolically more active than fat tissue, burning more calories at rest. Even a few extra pounds of muscle can increase your daily BMR by 10-20 calories.