BMR Calculator — Check Your Basal Metabolic Rate

Q: What's the difference between BMR and TDEE?

BMR is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) is your total calorie burn including all physical activity. TDEE is calculated by multiplying your BMR by an activity factor. For example, a moderately active person's TDEE is roughly 1.55 times their BMR.

BMR is an estimate based on the Mifflin-St Jeor equation. Individual metabolism varies based on genetics, body composition, and other factors. Talk to a clinician for personalized guidance.

Understanding Your Result

What does your basal metabolic rate mean?

Basal metabolic rate (BMR) is the number of calories your body needs to perform its most basic life-sustaining functions — breathing, circulating blood, regulating temperature, and producing cells. It represents the energy your body would burn if you did absolutely nothing for 24 hours.

This calculator uses the Mifflin-St Jeor equation, which is widely considered the most accurate BMR formula for most adults. The formula accounts for your weight, height, age, and sex to produce a personalized estimate.

For most adults, BMR falls somewhere between 1,200 and 2,400 calories per day, though this varies significantly based on body size, composition, and age. Your BMR typically accounts for 60–75% of your total daily calorie burn — the rest comes from physical activity and the thermic effect of food (digestion).

BMR is distinct from your total daily energy expenditure (TDEE), which includes all physical activity. To estimate TDEE, your BMR is multiplied by an activity factor. The table above shows your estimated TDEE at five common activity levels. You can also use our BMI calculator to assess your weight status alongside your metabolic rate.

Important Context

What BMR doesn't tell you

BMR is a useful estimate, but it has limitations worth understanding. Like any formula-based tool, it simplifies a complex biological process.

It doesn't account for body composition. The Mifflin-St Jeor equation uses total body weight, not lean mass versus fat mass. Since muscle tissue burns more calories at rest than fat tissue, two people with the same weight, height, age, and sex can have meaningfully different BMRs depending on their muscle-to-fat ratio.

It doesn't capture metabolic adaptation. When you lose weight — especially through calorie restriction — your metabolism can slow more than the formula predicts. This is known as adaptive thermogenesis, and it's one reason weight loss can plateau over time. Medical supervision helps identify and address these plateaus.

It varies by individual. Genetics, thyroid function, hormonal status, sleep quality, and even medications can influence your actual resting metabolic rate. The Mifflin-St Jeor equation provides a population-level estimate, not a precise individual measurement.

At PEAK, we use metabolic data alongside lab work, health history, body composition, and your personal goals to build a complete picture. An estimate is a starting point — clinical assessment tells the full story.

BMR & Weight Management

How BMR relates to weight loss

Your BMR is the metabolic floor — the baseline number of calories your body needs just to function. Understanding it is important because it helps establish how many calories you actually need each day, which is essential for safe and sustainable weight loss.

Weight loss requires a calorie deficit. To lose weight, you need to consume fewer calories than your TDEE (not your BMR). The key is creating a moderate deficit — typically 500 to 750 calories below TDEE — that promotes fat loss without triggering excessive metabolic slowdown or muscle loss.

Eating below your BMR is generally not recommended. Consistently consuming fewer calories than your basal metabolic rate can signal to your body that it's in a state of starvation. This can lead to muscle loss, nutrient deficiencies, hormonal disruption, and a further reduction in metabolic rate — making future weight loss harder.

Metabolism adapts as you lose weight. As your body gets smaller, your BMR decreases. This is a normal physiological response, but it means your calorie needs shift over time. This is one reason medically supervised weight loss programs — like those at PEAK — include ongoing monitoring and treatment adjustments. GLP-1 medications, for example, work in part by reducing appetite and improving metabolic signaling, helping patients maintain a sustainable deficit.

Muscle preservation matters. Since lean muscle mass is a primary driver of BMR, maintaining muscle during weight loss helps keep your metabolism from dropping too quickly. This is why PEAK's approach includes nutrition counseling focused on adequate protein intake and guidance on strength training.

Common Questions

Frequently asked questions about BMR

What is BMR?

Basal metabolic rate (BMR) is the number of calories your body burns at complete rest to maintain basic life-sustaining functions like breathing, circulation, cell production, and temperature regulation. It represents the minimum energy your body needs to function over a 24-hour period. BMR is different from TDEE, which includes calories burned through physical activity.

How is BMR calculated?

This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate BMR formula for most adults. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5. For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161. The formula converts your imperial measurements to metric before calculating.

What's the difference between BMR and TDEE?

BMR is the calories your body burns at complete rest — just to keep your organs functioning. TDEE (Total Daily Energy Expenditure) is your total calorie burn including all physical activity, from walking to workouts. TDEE is calculated by multiplying your BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extra active). For weight management purposes, TDEE is the more actionable number because it reflects your actual daily calorie needs.

Does BMR change as you lose weight?

Yes. As you lose weight, your BMR typically decreases because your body requires less energy to maintain a smaller mass. This is one reason weight loss can plateau over time — your body adapts to the new calorie intake. This is also why medical supervision is valuable during weight loss. At PEAK, clinicians can adjust your treatment plan as your metabolism adapts, helping you continue to make progress safely.

How does age affect BMR?

BMR generally decreases with age, primarily due to a gradual loss of lean muscle mass and changes in hormonal activity. After age 20, BMR typically declines by about 1–2% per decade. This is one reason why maintaining muscle through strength training and adequate protein intake becomes increasingly important as you age.

Can you increase your BMR?

Yes. The most effective way to increase BMR is by building lean muscle mass through strength training, since muscle tissue burns more calories at rest than fat tissue. Adequate protein intake, quality sleep, and staying well-hydrated also support healthy metabolic function. Some medical treatments can also affect metabolic rate — your clinician can discuss how specific medications may influence your metabolism.

Why does BMR matter for weight loss?

Understanding your BMR helps establish a safe and effective calorie target for weight loss. Eating significantly below your BMR can slow your metabolism, cause muscle loss, and undermine long-term results. A clinician-guided approach uses your BMR as a baseline to create a sustainable plan that preserves muscle while promoting fat loss. At PEAK, your registered dietitian and medical provider work together to set calorie and nutrition targets based on your individual metabolic profile.

What does your basal metabolic rate mean?

What BMR doesn't tell you

How BMR relates to weight loss

Frequently asked questions about BMR

Understanding your metabolism helps your provider and dietitian build a plan that fits your body.