BMR Calculator: Build Muscle and Lose Fat with This Calculator

by Nader Qudimat
Updated June 11, 2023

Have you ever wondered how many calories your body needs to simply exist?

That's where the Basal Metabolic Rate (BMR) comes in.

It's a crucial factor in understanding your body's needs, planning your diet, and setting fitness goals.

Use the calculator below to find out your BMR:

BMR Calculator (IMPERIAL)




BMR Calculator (METRIC)




What Activity Levels Mean

  1. Sedentary: This level is for individuals who do not engage in regular exercise at the gym. Their lifestyle might involve minimal physical activity, such as light stretching or very casual use of gym equipment less than 2 days per week.

  2. Lightly Active: This level is for individuals who engage in light exercise at the gym 2-3 days per week. This might include activities like light cardio on a treadmill or elliptical, or light weight training.

  3. Moderately Active: This level is for individuals who participate in moderate-intensity gym workouts 3-5 days per week. This could include activities like moderate weight lifting, regular use of resistance machines, or moderate-intensity group fitness classes.

  4. Very Active: This level is for individuals who engage in high-intensity gym workouts 6-7 days per week. This could include activities like heavy weight lifting, high-intensity interval training (HIIT), or advanced fitness classes.

  5. Extra Active: This level is for individuals who engage in very intense gym workouts or who are training for a specific athletic event. This could include activities like intense weightlifting programs, advanced HIIT sessions, or specialized athletic training.

Understanding BMR

Understanding BMR

Basal Metabolic Rate, or BMR, is the number of calories your body needs to perform basic functions, like breathing and maintaining body temperature, while at rest.

It's essentially the minimum energy requirement to keep the lights on in your body.

Factors such as age, gender, weight, and height all influence your BMR.

The Science Behind BMR

BMR is typically calculated using one of two formulas: the Harris-Benedict formula or the Mifflin St Jeor formula. Both take into account your height, weight, age, and gender, but they use slightly different calculations.

The Harris-Benedict formula is a bit older and tends to overestimate calorie needs slightly, while the Mifflin St Jeor formula, developed in the 1990s, is often considered more accurate.

How to Calculate Your BMR

Calculating your BMR is a straightforward process if you know your height, weight, age, and gender.

Here's a simplified version of how a BMR calculator works:

  1. Input your height, weight, age, and gender.
  2. The calculator above uses the Mifflin St Jeor formula to estimate your BMR.
  3. The result is the estimated number of calories you'd burn if you were to do nothing but rest for 24 hours.

Remember, this is an estimate.

For a more accurate figure, consider consulting with a healthcare professional.

Applying Your BMR

Knowing your BMR can help you make informed decisions about your diet and fitness routine.

For example, if you're looking to lose weight, you'll want to consume fewer calories than your BMR plus the calories you burn through activity.

If you're looking to gain muscle, you'll likely need to consume more.


Why is knowing my BMR important?

Knowing your BMR can help you create a diet plan that aligns with your fitness goals, whether that's losing weight, gaining muscle, or maintaining your current weight.

Can I change my BMR?

While factors like age and height are fixed, you can influence your BMR by gaining muscle mass, which burns more calories at rest than fat.

What factors can influence my BMR?

Several factors can influence your BMR, including:

  • Age: As you get older, your BMR generally decreases.
  • Gender: Men typically have a higher BMR than women because they usually have more muscle mass.
  • Weight: The more you weigh, the higher your BMR, as your body requires more energy to function.
  • Body Composition: Muscle burns more calories at rest than fat, so the more muscle mass you have, the higher your BMR.
  • Temperature: Both the temperature of your environment and your body can affect your BMR. If your body is cold, for example, it has to work harder to maintain its normal temperature and thus burns more calories.
  • Diet: Starvation or serious abrupt calorie reduction can dramatically decrease your BMR by up to 30%.

Can I increase my BMR?

Yes, you can increase your BMR by gaining muscle mass. Muscle burns more calories at rest than fat does, so the more muscle you have, the higher your BMR will be. Regular strength training and consuming enough protein can help you build muscle.

Does my BMR change as I lose weight?

Yes, as you lose weight, your BMR typically decreases. This is because your body requires less energy to function as its mass decreases.

This is why people often find they need to decrease their calorie intake or increase their physical activity over time to continue losing weight.

How often should I recalculate my BMR?

If you're using your BMR to inform your diet and exercise routine, it's a good idea to recalculate it every few months, especially if you've been losing or gaining weight. This will help ensure that you're consuming the right number of calories to meet your goals.

Why is my actual weight different from the weight predicted by my calorie intake and BMR?

There are many factors that can influence your weight, including water retention, muscle gain, and changes in body composition.

Additionally, the formulas used to calculate BMR and calorie needs are estimates and may not perfectly reflect your actual calorie needs.

If your actual weight is different from what's predicted based on your calorie intake and BMR, it might be worth consulting with a healthcare professional or a dietitian.

Bottom Line

Understanding your BMR is a key step in taking control of your health and fitness.

By calculating your BMR and using it to inform your diet and exercise decisions, you can work towards your goals in an informed and effective way.

by Nader Qudimat

Forged by iron and cold steel, I'm Nader, a mid-30s natural bodybuilder. Once a 100lb skinny guy, I've transformed into a 200lb muscular athlete with over 15 years of lifting experience. Today, I leverage my transformation and extensive experience to guide countless individuals on their fitness journeys.

Click here to check out my 12 year transformation: Natural 12 Year Transformation

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