BMR Calculator
Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation. Find how many calories your body burns at rest.
Our free BMR Calculator determines your Basal Metabolic Rate — the number of calories your body burns at complete rest just to keep you alive. Breathing, circulating blood, maintaining body temperature, and repairing cells all… Fill in the fields and see your result. Everything is computed on your device—we don't collect or store your inputs.
About This Calculator
Our free BMR Calculator determines your Basal Metabolic Rate — the number of calories your body burns at complete rest just to keep you alive. Breathing, circulating blood, maintaining body temperature, and repairing cells all require energy, and BMR accounts for 60-75% of the calories you burn every day. Knowing your BMR is the essential first step in any weight-loss, weight-gain, or maintenance plan because it tells you the absolute minimum calories your body needs. Enter your gender, age, height, and weight and get an accurate BMR estimate using the Mifflin-St Jeor equation, which studies have shown to be the most reliable formula for modern populations.
How It Works
The calculator applies the Mifflin-St Jeor equation: for men BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5; for women BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161. The result is your resting calorie burn in kilocalories per day. To find your Total Daily Energy Expenditure (TDEE), multiply BMR by an activity factor (1.2 for sedentary up to 1.9 for very active). The TDEE is the number you use for diet planning — eat below it to lose weight, at it to maintain, or above it to gain.
How to Use
- Enter your values in the calculator fields above
- Click the calculate button or let the calculator auto-update
- Review your results instantly
- Adjust values as needed to see different scenarios
Frequently Asked Questions
What exactly is BMR?
BMR (Basal Metabolic Rate) is the energy your body uses at complete rest in a thermally neutral environment after 12 hours of fasting. It covers core functions like heartbeat, breathing, brain activity, and cell repair. For most people BMR is between 1,200 and 2,000 calories per day, depending on size, age, and gender.
How is BMR different from TDEE?
BMR is calories burned at rest only. TDEE (Total Daily Energy Expenditure) includes your BMR plus calories burned through daily movement, exercise, and digesting food. TDEE = BMR x activity factor. For diet planning you should use TDEE, not BMR, as your baseline.
Can I eat below my BMR to lose weight faster?
It is generally not recommended. Eating below BMR for extended periods can slow your metabolism, cause muscle loss, reduce energy levels, and lead to nutrient deficiencies. A safe approach is to eat 500-1,000 calories below your TDEE (not BMR), which produces 0.5-1 kg of weight loss per week while preserving muscle and health.
Why does BMR decrease with age?
As you age, you tend to lose muscle mass (sarcopenia) and hormonal changes slow your metabolism. The Mifflin-St Jeor equation accounts for this with the age variable. Strength training and maintaining an active lifestyle can partially offset the decline.
How accurate is this formula?
The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population, typically within 10% of measured values. Individual variation exists due to genetics, body composition, and hormones. For a precise measurement, clinical indirect calorimetry is the gold standard.
Why Use Our Free BMR Calculator Online?
Our BMR Calculator gives you a quick, private check without an account. Enter your details and get an instant result. All processing happens locally, so we don't see or store your health-related inputs. For medical decisions, always consult a healthcare provider; this tool is for general guidance only.