Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions (breathing, circulation, cell production) while at rest. It represents energy expenditure at complete rest.

Which formula is best to calculate BMR?

There is no single 'best' formula; the Mifflin–St Jeor formula is widely used and considered accurate for the general population. Harris–Benedict and Katch-McArdle are other common formulas; choice may depend on available inputs (e.g., body fat % for Katch-McArdle).

TDEE (Total Daily Energy Expenditure) is an estimate of total daily calories burned — BMR multiplied by an activity factor (sedentary, moderate, active, etc.).

Can BMR calculators be trusted?

BMR calculators provide estimates. Individual needs vary due to genetics, muscle mass, health conditions, and measurement inaccuracies. Use results as a starting point and consult a professional for personalized plans.

How often should I recalculate my BMR?

Recalculate when weight, age, or body composition changes significantly (e.g., every 3–6 months) or when starting a new training/nutrition program.

Yes. BMR generally declines with age due to lower muscle mass and metabolic changes.

Do I need to measure body fat to use this tool?

No. Most formulas (Mifflin–St Jeor, Harris–Benedict) use weight, height, age and sex. Katch-McArdle uses lean body mass (requires body fat %). If you do not know body fat%, you can use the other formulas.

BMR (Basal Metabolic Rate) Calculator

BMR estimates the calories your body needs at complete rest. Use this tool to get Mifflin–St Jeor and Harris–Benedict estimates and a TDEE (activity-adjusted) recommendation.

Gender

Age (years)

Units

Height (cm)

Weight (kg)

Formula (results shown for each)

Activity Level (for TDEE)

BMR — Quick facts

BMR declines with age and with loss of lean muscle mass.
Muscle tissue burns more calories at rest than fat — strength training helps increase BMR.
Use BMR as baseline; TDEE (BMR × activity factor) gives full daily calorie needs.
For weight loss aim for a moderate calorie deficit (250–700 kcal/day) based on TDEE; consult a professional before large changes.

About BMR & How It’s Calculated

Below are common formulas your results will show. These are estimates — individual needs may vary.

Mifflin–St Jeor (1990):

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Revised Harris–Benedict (1984):

Men: BMR = 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age + 88.362
Women: BMR = 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age + 447.593

Katch–McArdle:

BMR = 370 + (21.6 × LeanBodyMass(kg)) — requires body fat % to estimate lean mass.

TDEE example: If your BMR is 1500 kcal and activity factor is 1.55 → TDEE ≈ 2325 kcal/day.

When to use which formula?

Mifflin–St Jeor: Best general-purpose for most adults.
Harris–Benedict: Older formula, still useful for comparison.
Katch–McArdle: Best if you know lean body mass (body fat% available).

Basal Metabolic Rate — Detailed Guide

BMR is the baseline number of calories required to keep your body functioning at rest. It does not include activity, digestion, or exercise. Below is a deeper look — this content helps search engines understand context and improves ranking for health queries.

What affects BMR?

Lean body mass: More muscle → higher BMR.
Age: BMR declines with age.
Sex: On average, males have higher BMR due to greater muscle mass.
Genetics & hormones: Thyroid function and other hormones affect resting metabolism.
Body size: Taller and heavier individuals usually have higher BMR.

How to use BMR and TDEE in planning?

Calculate BMR with a formula.
Multiply by activity factor to get TDEE.
For weight loss: create a caloric deficit (e.g., 10–20% below TDEE) — prefer sustainable deficits.
For muscle gain: consume slight calorie surplus + resistance training.
Always prioritize protein and micronutrient-rich foods for health.

Limitations

These formulas are estimates. Body composition, medical conditions, medications, and measurement errors can change real requirements. Use results as a starting point and refine using tracking (weight, body measurements) over weeks.

Frequently Asked Questions (FAQ)

Is BMR the same as calories burned?

BMR is only calories burned at complete rest. It does not include calories burned by activity, digestion (thermic effect of food) or exercise. TDEE includes these by applying an activity multiplier.

Which activity factor should I choose?

Choose the factor that best matches your typical daily routine: sedentary for desk jobs, lightly active for light exercise, moderate for several workouts per week, and very/extra active for heavy training or physically demanding jobs.

How accurate is body fat percentage input?

Body fat measurements vary by method. Calipers, bioelectrical impedance, DEXA, and other methods have different accuracies. Katch–McArdle relies on lean mass estimates, so inaccurate body fat leads to inaccurate BMR for that formula.

Can I use BMR for children or pregnant women?

These formulas are designed for adults. For children, adolescents, pregnant or breastfeeding women, consult a healthcare professional for suitable assessments.

Do I need to be fasting to measure BMR?

Clinical BMR measurement often happens after overnight fasting and sleep. Online calculators give estimates without fasting; they are still useful for planning.