BMR Calculator

What this BMR calculator does

Basal metabolic rate (BMR) is the energy your body uses at rest to maintain breathing, circulation, cell growth, and other basic functions. This calculator estimates BMR from age, sex, height, and weight, then multiplies it by common activity levels to estimate daily calorie needs.

Three formulas are available. Mifflin-St Jeor is the default for most adults. Revised Harris-Benedict is an older equation that some people still use. Katch-McArdle uses lean body mass and requires a body fat percentage.

How to use this calculator

1. Choose US or metric units.
2. Enter age, sex, height, and weight.
3. Choose a BMR formula.
4. If you choose Katch-McArdle, enter your body fat percentage.
5. Click Calculate to see BMR and calories at each activity level.

The default example is a 25-year-old man who is 5 ft 10 in tall and weighs 160 lb, using Mifflin-St Jeor.

BMR formulas

Mifflin-St Jeor (men):   10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Mifflin-St Jeor (women): 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Revised Harris-Benedict (men):
  88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age
Revised Harris-Benedict (women):
  447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age

Katch-McArdle: 370 + 21.6 × lean body mass(kg)

Activity multipliers:

What the results mean

• BMR: calories your body would use at complete rest. The default example is 1,717 Calories/day.
• Activity calories: BMR multiplied by an activity factor. These estimate total daily energy expenditure for that activity pattern.
• Formula: the equation used. Different formulas can differ by a hundred calories or more.

The activity table is a planning guide. It is not a measurement of the calories you burn on a specific day.

Assumptions and limitations

The formulas are population estimates. They do not account for medical conditions, medications, pregnancy, lactation, very high muscle mass, or changes in body composition. Katch-McArdle requires a body fat estimate; if that estimate is wrong, the result will be wrong.

Self-reported activity can be inaccurate. Many people overestimate exercise and underestimate sedentary time. Use the activity level that matches a typical week, not your best week.

Frequently asked questions

Which BMR formula should I use?

Mifflin-St Jeor is a reasonable default for most adults. Katch-McArdle can be useful if you have a reliable body fat measurement. Harris-Benedict is older and tends to produce slightly different estimates.

Is BMR the same as calories burned?

No. BMR is the resting component. Total daily energy expenditure also includes movement, exercise, digestion, and other activity. The activity table estimates that total.

Does BMR decrease with age?

Yes, on average, partly because lean mass tends to decline with age. The formulas include age as a variable, but individual changes vary.

Can I use this to plan weight loss?

Use it as a starting estimate, then track actual weight and intake for several weeks. A clinician or registered dietitian can help set a safe target, especially if you have a medical condition.

Source

References:

• National Institute of Diabetes and Digestive and Kidney Diseases — Body Weight Planner
• National Heart, Lung, and Blood Institute — Calculate your BMI

Disclaimer

This calculator is for informational and educational purposes only. It is not medical advice. Calorie needs vary. Consult a qualified health professional before making significant changes to diet or exercise.