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BMR Calculator
Estimate your basal metabolic rate, the calories your body burns at rest, using the Mifflin-St Jeor, Revised Harris-Benedict or Katch-McArdle formula. Then see your daily calorie needs and calorie targets for weight loss, maintenance or gain.
BMR Calculator
Your Result
Basal metabolic rate: –
| Formula | BMR |
|---|---|
| Mifflin-St Jeor | – |
| Revised Harris-Benedict | – |
| Katch-McArdle | – |
| Daily calories to maintain weight | TDEE |
|---|---|
| Sedentary (x 1.2) | – |
| Light (x 1.375) | – |
| Moderate (x 1.55) | – |
| Very active (x 1.725) | – |
| Extra active (x 1.9) | – |
| Calorie targets at your activity level | Per day |
|---|---|
| Maintain weight | – |
| Mild weight loss (−250) | – |
| Weight loss (−500) | – |
| Mild weight gain (+250) | – |
| Weight gain (+500) | – |
Estimates for healthy adults. Not suitable during pregnancy or breastfeeding. Avoid eating below 1,200 kcal (women) or 1,500 kcal (men) a day unless a doctor supervises you.
What Is BMR (Basal Metabolic Rate)?
Basal metabolic rate (BMR) is the amount of energy, measured in calories (kcal) per day, that your body needs to stay alive while completely at rest. It covers the work your body does without you thinking about it: breathing, pumping blood, growing and repairing cells, keeping your organs running and maintaining body temperature.
For most people BMR accounts for the largest share of the calories they burn each day, commonly cited as around 60 to 70 percent. That is why it is the starting point for almost every calorie plan. If you know your BMR, you can work out your total daily energy needs and set realistic targets for maintaining, losing or gaining weight.
How to Use This BMR Calculator
- Choose Metric or US units, and select Male or Female.
- Enter your age, height and weight.
- Pick a formula. Mifflin-St Jeor is the default. If you know your body fat percentage, enter it and choose Katch-McArdle.
- Choose your activity level to see your daily calorie needs (TDEE) and calorie targets for weight loss or gain.
The calculator shows all three formulas side by side so you can compare them. All calculations happen in your browser, and nothing is stored or sent anywhere.
BMR Formulas
This calculator uses three well-known equations. In each, weight is in kilograms, height is in centimetres and age is in years.
Mifflin-St Jeor equation (1990)
Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
Revised Harris-Benedict equation (Roza and Shizgal, 1984)
Women: BMR = 447.593 + (9.247 × weight) + (3.098 × height) − (4.330 × age)
Katch-McArdle formula
Which BMR Formula Should You Use?
| Formula | Best for | Needs |
|---|---|---|
| Mifflin-St Jeor | Most healthy adults. Generally considered the most reliable of the three for the general population. | Sex, age, height, weight |
| Revised Harris-Benedict | A useful comparison. It tends to give a slightly higher result than Mifflin-St Jeor. | Sex, age, height, weight |
| Katch-McArdle | Lean or muscular people who know their body fat percentage, since it is based on lean mass. | Weight and body fat % |
If you do not know your body fat percentage, use Mifflin-St Jeor. You can estimate your body fat with our Body Fat Calculator.
Worked Example
Take a 35-year-old man who is 180 cm tall, weighs 80 kg and has 20 percent body fat.
- Mifflin-St Jeor: (10 × 80) + (6.25 × 180) − (5 × 35) + 5 = 1,755 kcal/day
- Revised Harris-Benedict: 88.362 + (13.397 × 80) + (4.799 × 180) − (5.677 × 35) = 1,825 kcal/day
- Katch-McArdle: lean mass = 80 × 0.80 = 64 kg, so 370 + (21.6 × 64) = 1,752 kcal/day
The three results land within a few percent of each other, which is typical. If he exercises three to five days a week (moderate activity, multiplier 1.55), his estimated daily needs using Mifflin-St Jeor are about 2,720 kcal.
For a 30-year-old woman who is 165 cm and 65 kg, Mifflin-St Jeor gives (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 1,370 kcal/day.
BMR vs RMR vs TDEE
- BMR is measured under strict conditions: after fasting, a full night of sleep and in a thermoneutral room.
- RMR (resting metabolic rate) is measured under more relaxed conditions and is usually slightly higher. In everyday use the two terms are often swapped, and the formulas above are really estimating RMR.
- TDEE (total daily energy expenditure) is everything you burn in a day. It combines BMR, the thermic effect of food (energy used to digest meals), non-exercise activity such as walking and fidgeting, and planned exercise.
Activity Multipliers and Your TDEE
To turn BMR into TDEE, multiply it by an activity factor:
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1 to 3 days a week | 1.375 |
| Moderately active | Moderate exercise 3 to 5 days a week | 1.55 |
| Very active | Hard exercise 6 to 7 days a week | 1.725 |
| Extra active | Very hard exercise, or a physical job plus training | 1.9 |
People tend to overestimate their activity, so if you are between two levels, choose the lower one and adjust based on real results over a few weeks.
Using BMR to Plan Weight Loss, Maintenance or Gain
Your TDEE is the number of calories you need to maintain your current weight. To change weight, you eat below or above it.
- Weight loss: a deficit of about 250 to 500 calories a day is a common, sustainable starting point. As a rough rule, 7,700 calories is about 1 kg of body weight (about 3,500 calories per pound), so a 500-calorie daily deficit leads to roughly 0.5 kg (1 lb) a week.
- Weight gain: a surplus of 250 to 500 calories a day, combined with strength training, supports gradual gain.
- Safety floor: it is generally advised not to eat below 1,200 calories a day (women) or 1,500 (men) without medical supervision. Very low intakes can cause nutrient shortfalls and muscle loss.
These figures are estimates. Your body adapts, so track your weight and energy levels for two to three weeks and adjust. If you are planning a significant change, speak to a doctor or registered dietitian. You can also use our BMI Calculator to see where your weight sits for your height.
What Affects Your BMR?
- Body composition: muscle burns more energy at rest than fat, so more lean mass means a higher BMR.
- Size: larger, taller bodies need more energy.
- Age: BMR tends to decline with age, largely because of loss of muscle.
- Sex: men usually have a higher BMR than women of the same age and weight because they carry more lean mass on average.
- Genetics: some people naturally burn more or less than the formulas predict.
- Hormones: thyroid conditions can raise or lower metabolic rate significantly.
- Pregnancy and breastfeeding: energy needs rise.
- Temperature and illness: fever, injury, and very hot or cold environments can increase energy use.
- Dieting: prolonged, severe calorie restriction can lower BMR as the body adapts.
How to Support a Healthy Metabolism
You cannot change your genetics or age, but a few habits help you keep your BMR as high as it can be.
- Strength train two or more times a week to build and keep muscle.
- Eat enough protein. Protein has a higher thermic effect than fat or carbohydrate and supports muscle.
- Avoid crash diets. Large, long-term deficits can reduce lean mass and slow metabolism.
- Move through the day. Walking, standing and general activity add to your TDEE.
- Sleep well. Poor sleep affects appetite hormones and energy levels.
Limitations of BMR Calculators
BMR equations estimate the average result for groups of people. Individual results can differ by 10 percent or more because of genetics, body composition, hormones and health conditions. The equations are designed for healthy adults and are not suitable for children, pregnant or breastfeeding women, or people with medical conditions that affect metabolism. The only way to measure BMR accurately is indirect calorimetry in a clinic. Use your result as a starting point and adjust it with real-world progress.
Medical disclaimer: this calculator is for general information only and is not medical or dietary advice. Speak to a qualified healthcare professional before changing your diet or exercise routine. Equations: Mifflin et al. (1990), Roza and Shizgal (1984) and Katch and McArdle.
Frequently Asked Questions
What is BMR?
BMR stands for basal metabolic rate. It is the number of calories your body needs to keep you alive at complete rest, covering functions like breathing, circulation, cell repair and temperature control.
How do I calculate my BMR?
Use a validated equation that takes your sex, age, height and weight. Our calculator offers three: Mifflin-St Jeor, Revised Harris-Benedict and Katch-McArdle, which also uses body fat percentage.
Which BMR formula is the most accurate?
For most people, Mifflin-St Jeor is considered the most reliable of the three. Katch-McArdle can be better for lean or very muscular people if you know your body fat percentage. Every formula is an estimate.
What is the difference between BMR and RMR?
BMR is measured under strict conditions: fasted, rested and at a comfortable temperature. Resting metabolic rate (RMR) is measured under looser conditions and is usually a little higher. Calculators often use the two terms interchangeably.
What is the difference between BMR and TDEE?
BMR is the energy you burn at rest. TDEE, or total daily energy expenditure, adds the energy used for digesting food, daily movement and exercise. TDEE is your BMR multiplied by an activity factor.
How many calories should I eat to lose weight?
A common starting point is to eat about 500 calories below your TDEE, which tends to lead to a loss of roughly 0.5 kg (1 lb) per week. This is an approximation, and it is generally advised not to go below 1,200 calories for women or 1,500 for men without medical supervision.
Does BMR change with age?
Yes. BMR generally declines with age, mainly because people tend to lose muscle mass over time. Staying active and keeping muscle through strength training helps.
Do men have a higher BMR than women?
On average, yes, because men typically have more lean muscle mass and larger bodies. The equations include a sex-based adjustment for this reason.
Can I increase my BMR?
You can raise it modestly by building muscle through resistance training, eating enough protein and avoiding extreme calorie cuts, which can lower your metabolic rate. Genetics and age also play a role.
Is this BMR calculator suitable during pregnancy or for children?
No. The equations are designed for healthy adults. Pregnancy, breastfeeding, childhood and some medical conditions change energy needs, so speak to a healthcare professional.