Calorie Calculator (BMR)
Estimate your Basal Metabolic Rate — the number of calories your body burns at complete rest — using the widely accepted Mifflin-St Jeor equation. Enter your age, sex, height, and weight in metric or imperial units for an instant result. Use this as a starting point for understanding your daily energy needs.
How It Works
The Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production, and temperature regulation — while at complete rest. It does not account for any physical activity.
The Mifflin-St Jeor equation is the most widely validated BMR formula for general use and is recommended by the Academy of Nutrition and Dietetics. It was developed in 1990 from a study of 498 participants and outperforms older formulas such as the Harris-Benedict equation across a wide range of body types.
Mifflin-St Jeor Formula:
Male BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Female BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
The only difference between male and female is the constant at the end (+5 vs −161), reflecting average differences in body composition.
Worked example (male, 30 years, 75 kg, 175 cm):
BMR = (10 × 75) + (6.25 × 175) − (5 × 30) + 5
BMR = 750 + 1093.75 − 150 + 5
BMR = 1698.75 calories/day
Wait — the answer is 1698.75? Yes. This is the number of calories burned at complete rest. Most people burn significantly more once activity is factored in. See the TDEE Calculator for the activity-adjusted figure.
Imperial unit conversion used internally:
Weight: pounds × 0.453592 = kilograms
Height: (feet × 12 + inches) × 2.54 = centimetres
Limitations: BMR formulas are population-level estimates. Individual results vary based on genetics, body composition (muscle vs fat percentage), hormonal factors, and medical conditions. Athletes may have a meaningfully higher BMR than predicted; individuals with thyroid disorders may differ significantly. Always consult a healthcare professional for personalised nutrition advice.
Frequently Asked Questions
What is BMR and why does it matter?
BMR stands for Basal Metabolic Rate — the calories your body burns just to stay alive at rest. It represents the floor of your daily caloric needs. Understanding your BMR helps you set realistic calorie targets for weight loss, maintenance, or gain when combined with an activity multiplier (see the TDEE Calculator).
Why is Mifflin-St Jeor used instead of Harris-Benedict?
The Harris-Benedict equation was derived in 1918 and tends to overestimate BMR, especially in overweight individuals. Mifflin-St Jeor (1990) was validated on a larger and more diverse population and is consistently more accurate for modern body compositions. Most registered dietitians now use Mifflin-St Jeor as the standard starting point.
Why are there different formulas for males and females?
On average, males have more lean muscle mass and less body fat than females at the same height and weight. Muscle tissue burns more calories at rest than fat tissue, so males typically have a higher BMR. The Mifflin-St Jeor equation captures this with different constants (+5 for male, −161 for female).
Is this result the number of calories I should eat per day?
No. BMR is the number of calories needed at complete rest. Most people are not bedridden, so you need to multiply BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE). Use the TDEE Calculator on this site for the activity-adjusted figure before setting a calorie target.
How accurate is this estimate?
Population-level studies show Mifflin-St Jeor is accurate within roughly 10% for most healthy adults. Individual variation due to genetics, body composition, hormones, and metabolic conditions can push results outside that range. Treat the result as a starting estimate and adjust based on real-world observations over 2–4 weeks.