BMR & Body Fat Calculator

Calculate BMR · TDEE · Body Fat Percentage in one place

Add body fat measurement inputs

How to Use

Enter Basic Information

Input your gender, age, height, and weight.

Select Activity Level

Choose the activity level that matches your exercise frequency and intensity.

Add Body Fat Inputs (Optional)

For more accurate results, toggle on body fat measurement and enter waist, neck, and hip measurements.

Calculate

Press Calculate to see your BMR, TDEE, target calories, and body fat results.

Use Cases

  • Setting daily calorie goals for dieting or bulking
  • Reference for personal trainers and nutritionists when designing meal plans
  • Tracking body fat changes before and after health check-ups
  • Using as baseline data when designing workout programs
  • Planning calorie intake for endurance sports like marathons or triathlons

Tips

  • The Mifflin-St Jeor formula is most accurate for the general population.
  • If you know your body fat percentage, prioritize the Katch-McArdle formula.
  • When losing weight, don't cut more than 500 kcal below TDEE to avoid muscle loss.
  • Overestimating activity level leads to an inflated TDEE calculation.
  • Measure neck and waist with a tape measure horizontally, breathing normally.
  • The US Navy body fat formula has a ±3~4% margin of error; use it as a reference.

Frequently Asked Questions

Q. What is the difference between BMR and TDEE?

A. BMR (Basal Metabolic Rate) is the minimum calories needed to maintain basic life functions (breathing, heartbeat, temperature regulation) while at complete rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor, representing total calories burned per day. To maintain weight, you should consume calories equal to your TDEE.

Q. Which of the three BMR formulas should I trust?

A. The Mifflin-St Jeor formula is generally considered most accurate for modern adults. The Harris-Benedict formula is older and tends to run slightly high. If you know your body fat percentage, the Katch-McArdle formula is most accurate. Prioritize Katch-McArdle when body fat input is provided.

Q. Why are waist, neck, and hip measurements needed for body fat?

A. This calculator uses the US Navy method. Body fat correlates with body density, where waist circumference serves as a proxy for fat mass and neck circumference as a proxy for muscle mass. Women include hip measurements because fat distribution differs in the hip region. This method has a ±3~4% margin compared to DEXA scans.

Q. How much should I reduce calories for weight loss?

A. A deficit of 500 kcal/day below TDEE typically leads to about 0.5kg of weight loss per week. However, eating below your BMR can cause muscle loss, metabolic slowdown, and nutritional deficiency. A safe loss rate is 0.5~1.0kg per week; avoid extreme low-calorie diets.

Q. How do I choose my activity level?

A. Sedentary means mostly sitting with little to no exercise. Lightly active is 1~3 days of light exercise per week. Moderately active is 3~5 days of moderate exercise. Very active is 6~7 days of intense exercise. Extra active is training twice daily or having a physically demanding job. Most people fall under moderately active or below.

Q. Why is Lean Body Mass (LBM) important?

A. Lean Body Mass is your total weight minus fat — it includes muscle, bone, water, and organs. Since muscle burns more calories than fat, higher LBM means a higher BMR. Preserving muscle during a diet is critical for long-term weight management.

Q. My BMR seems low. How can I raise it?

A. BMR is primarily determined by muscle mass. Resistance training to build muscle is the most effective way to increase BMR. Extreme low-calorie diets can suppress BMR, so maintaining adequate calorie intake while exercising is recommended.

Q. Why do body fat categories differ by gender?

A. Women require more essential fat (about 10~13%) than men for hormonal function and reproductive health. Therefore, the same body fat percentage means different things for men and women, and the healthy range is higher for women.

Notice

  • This calculator is for reference only and may differ from clinical measurements (DEXA, bioelectrical impedance, etc.).
  • BMR formulas are developed for healthy adults; pregnant women, nursing mothers, adolescents, and those with certain conditions may need different references.
  • The US Navy body fat method has a ±3~4% margin of error.
  • Calorie targets vary based on individual health status, goals, and metabolic traits.
  • Consult a professional before attempting extreme low-calorie diets.

What is BMR (Basal Metabolic Rate)?

BMR (Basal Metabolic Rate) is the minimum energy required to sustain basic life functions (breathing, heartbeat, temperature regulation) while at complete rest. It accounts for about 60~75% of total daily calorie expenditure and varies by age, gender, height, weight, and muscle mass.

TDEE and Activity Multipliers

TDEE (Total Daily Energy Expenditure) is the total energy expended in a day, calculated by multiplying BMR by an activity multiplier. The multiplier ranges from 1.2 (sedentary) to 1.9 (extra active) across 5 levels.

US Navy Body Fat Method

Developed by the US Navy, this method estimates body fat using waist, neck, and hip circumferences. It requires no special equipment and has a ±3~4% margin versus DEXA scans. It is useful for tracking changes over time when measurements are taken consistently.

History and Differences of BMR Formulas

The Harris-Benedict formula was developed in 1919 and tends to overestimate slightly for modern adults due to the characteristics of the original study population. The Mifflin-St Jeor formula, developed in 1990, is based on a broader sample and is the most clinically recommended today. The Katch-McArdle formula uses Lean Body Mass directly, making it the most accurate of the three when body fat percentage is known.

Body Fat and Health

Body fat plays vital roles including energy storage, hormone production, organ protection, and temperature regulation. However, excessive body fat — especially visceral abdominal fat — increases risks of diabetes, cardiovascular disease, and hypertension. Maintaining an appropriate body fat percentage and exercising regularly are key to metabolic health.

BMR Formula Reference

Harris-Benedict (남/Male): 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Harris-Benedict (여/Female): 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)
Mifflin-St Jeor (남/Male): (10 × kg) + (6.25 × cm) − (5 × age) + 5
Mifflin-St Jeor (여/Female): (10 × kg) + (6.25 × cm) − (5 × age) − 161
Katch-McArdle: 370 + (21.6 × LBM), LBM = kg × (1 − BF%/100)

US Navy Body Fat Formula Reference

Male: 495 / (1.0324 − 0.19077 × log₁₀(허리−목) + 0.15456 × log₁₀(키)) − 450
Female: 495 / (1.29579 − 0.35004 × log₁₀(허리+엉덩이−목) + 0.22100 × log₁₀(키)) − 450

This calculator is provided for informational purposes only.

Results are estimates and may differ from actual amounts.

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