Introduction
Your Basal Metabolic Rate (BMR) is the number of calories your body burns each day just to stay alive. Even when you are sleeping or sitting still, your body uses energy to breathe, pump blood, and keep your organs working. Knowing your BMR helps you understand how many calories you need each day. This is useful whether you want to lose weight, gain weight, or stay the same. Our BMR Calculator uses proven formulas to give you a quick and accurate estimate based on your age, gender, height, and weight. Once you know your BMR, you can make smarter choices about how much to eat and plan a diet that fits your goals.
How to Use Our BMR Calculator
Enter your basic body details below to find out your Basal Metabolic Rate (BMR), the number of calories your body burns each day just to stay alive at rest.
Gender: Select whether you are male or female. Your body burns calories at different rates based on your sex, so this helps us pick the right formula for you.
Age: Enter your age in years. As you get older, your metabolism slows down, which means your body needs fewer calories at rest.
Weight: Enter your current body weight. You can use pounds or kilograms. People who weigh more need more energy just to keep their body running.
Height: Enter how tall you are. You can use feet and inches or centimeters. Taller people tend to have a higher BMR because they have more body mass to support.
Formula: Choose which BMR formula you want to use. The Mifflin-St Jeor equation is the default because a systematic review found it the most reliable of the common equations.6 The Harris-Benedict equation is an older but still popular option. If you know your body fat percentage, the Katch-McArdle formula uses your lean body mass instead of your total weight. All three give you a solid estimate of your daily calorie needs at rest.
What Is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate, or BMR, is the number of calories your body burns each day just to stay alive. Even when you are sleeping or sitting completely still, your body uses energy to breathe, pump blood, grow cells, and keep your brain working. BMR is the single biggest part of the calories you burn every day.
How Is BMR Calculated?
This calculator lets you choose from three well-known BMR formulas:
- Mifflin-St Jeor – Published in 1990 from indirect-calorimetry measurements in 498 healthy adults.1 It uses your weight, height, age, and gender to estimate BMR.
- Harris-Benedict (Revised) – One of the oldest BMR equations, first published by Harris and Benedict in 1918.2 The coefficients used here come from Roza and Shizgal's 1984 re-evaluation,3 as printed in a 2021 systematic review of prediction equations.4 It uses the same inputs as Mifflin-St Jeor.
- Katch-McArdle – This formula uses your lean body mass (weight minus fat) instead of total weight, so it requires your body fat percentage. The equation, 370 + 21.6 × lean mass, is the general prediction equation Cunningham published in 1991.5 It can be more useful for people who are very muscular or who know their body fat level.
Research published in the Journal of the American Dietetic Association found that the Mifflin-St Jeor equation predicted resting metabolic rate within 10% of measured values in more study participants than other formulas.6 That is why it is set as the default here.
BMR vs. TDEE: What's the Difference?
BMR only covers the calories you burn at rest. Your Total Daily Energy Expenditure (TDEE) adds in the calories you burn through walking, exercising, working, and even digesting food. TDEE is calculated by multiplying your BMR by an activity factor, which this calculator sets from 1.2 (sedentary) to 1.9 (extra active). Your TDEE is the number you actually need to pay attention to when planning how much to eat each day.
What Affects Your BMR?
Several factors raise or lower your BMR:
- Muscle mass – Muscle tissue burns more calories at rest than fat tissue. People with more muscle have a higher BMR. Strength training and proper protein intake are the most effective ways to build and maintain muscle.
- Age – BMR tends to fall with age, mainly because muscle mass declines by roughly 3% to 8% per decade after age 30.7
- Gender – Males generally have a higher BMR than females of the same weight because they tend to carry more muscle.
- Body size – Taller and heavier people have a higher BMR because there is more tissue for the body to maintain. You can check where your weight falls relative to your height using a standard BMI calculation, which is included in the results above.
- Genetics and hormones – Thyroid function, in particular, plays a big role in metabolic rate.
Using BMR and TDEE for Weight Management
Once you know your TDEE, you can set calorie goals based on what you want to achieve. Eating fewer calories than your TDEE creates a calorie deficit, which leads to weight loss. Eating more creates a surplus, which leads to weight gain. Federal obesity guidance puts a deficit of 500 to 1,000 calories per day at a loss of 1 to 2 pounds per week.8 The familiar figure of 3,500 calories per pound is a rule of thumb: a 2008 analysis found it roughly right for people starting with more than 30 kg of body fat and an overestimate for leaner people.9
The calculator above shows three deficit levels: mild, moderate, and aggressive. A mild deficit is easier to stick with long term, while an aggressive deficit produces faster results but can be harder to maintain and may increase the risk of muscle loss. Federal guidance sets supervised low-calorie diets at 1,000 to 1,200 calories per day for most women and 1,200 to 1,600 for men.8 This calculator's floors are 1,200 and 1,500, and going below them is something to do only with guidance from a doctor or registered dietitian.
To make your deficit sustainable, focus on the quality of your diet as well as the quantity. Getting enough fiber keeps you feeling full, adequate water intake supports metabolism and energy levels, and tracking your carbohydrate intake can help you fine-tune performance and satiety.
A Note on Accuracy
All BMR formulas provide estimates, not exact measurements. The true way to measure your metabolic rate is through a procedure called indirect calorimetry, which is done in a clinical setting. However, these equations give you a strong starting point. Track your weight and food intake over two to four weeks, then adjust your calories based on real results. If you are losing weight faster or slower than expected, shift your intake by 100 to 200 calories and reassess.