Free BMR Calculator - Basal Metabolic Rate

Based on peer-reviewed medical formulas. See our formulas & sources →

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Your body burns this many calories at rest

The Science Behind Baseline Calories

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest. Using the Mifflin-St Jeor equation — widely considered the most accurate BMR formula — men calculate BMR as: 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) + 5. Women: 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) - 161. A normal BMR for adult males is 1,400–1,800 kcal/day; for females, 1,200–1,500 kcal/day.

Here's the puzzle most people miss: even if you lay in bed all day without moving, your body still burns a fixed number of calories just to keep breathing, circulating blood, producing cells, and holding your temperature steady. That baseline — the minimum energy cost of staying alive — is your BMR, and it typically claims 60-75% of everything you burn in a day. Precisely because it is so large, small differences in age, gender, weight, height, and body composition can shift your daily calorie needs by hundreds.

Formula: Mifflin-St Jeor equation (1990). Source: Mifflin MD, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-247. Full methodology →

What Drives Your BMR Up or Down

Two similar people can have surprisingly different resting calorie burns, and the reasons are the same variables that shift as you age or change body composition. Some of these you control; some you do not.

Age: BMR formulas include a small age adjustment, but the old "1-2% cliff after 20" claim is outdated — a landmark 2021 analysis in Science (based on more than 6,400 doubly labeled water measurements) found daily energy expenditure stays stable from age 20 to 60. Most "middle-age slowdown" is lost muscle and lower activity, both reversible.
Gender: Males typically have a higher BMR than females due to greater muscle mass and larger body size. This calculator accounts for the difference in the formula.
Muscle mass: Muscle tissue is metabolically active and burns more calories at rest than fat tissue. People with more muscle mass have a higher BMR.
Body size: Larger individuals have a higher BMR because it takes more energy to sustain a bigger body. Both weight and height influence this.

Why Your BMR Is Not Your Diet

A common trap is treating the BMR number as your daily eating target — but this baseline only covers your resting needs, not the energy you burn moving through the day. To know how much you should actually eat, add your activity to your BMR to get TDEE (Total Daily Energy Expenditure). For weight loss, cut below your TDEE but stay above your BMR; for weight gain, overshoot your TDEE. Your BMR is the foundation of that math, not the final number you should be matching.

Why Muscle Raises Your BMR

Not all tissue burns calories at the same rate. Muscle is metabolically expensive — it requires energy even when you are doing nothing. This is why two people of the same weight can have very different BMRs depending on their body composition.

Muscle tissue: Burns approximately 6–7 kcal per pound per day at rest. A person carrying an extra 10 lbs of muscle compared to someone of the same weight burns roughly 60–70 more calories daily without any change in activity.
Body fat: Burns only about 2 kcal per pound per day at rest. Fat is energy storage tissue — it is designed to be metabolically quiet, not active.
The NEAT factor: Non-Exercise Activity Thermogenesis (NEAT) accounts for 15–30% of your daily calorie burn. Fidgeting, standing, walking to the car, and even typing all contribute. People with higher NEAT can burn 350+ more calories per day than sedentary individuals, even with identical BMRs.

This is why strength training indirectly raises your total daily calorie burn: more muscle means a higher BMR, and the activity of building that muscle often increases NEAT as well. Over time, this creates a compounding metabolic advantage that cardio alone does not replicate.

Frequently Asked Questions

What does a typical BMR actually look like?

A normal BMR for adult males typically ranges from 1,400 to 1,800 kcal/day, while for adult females it ranges from 1,200 to 1,500 kcal/day. These values vary based on age, weight, height, and body composition. A higher BMR means your body burns more calories at rest.

How do BMR and TDEE actually differ?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions like breathing and circulation. TDEE (Total Daily Energy Expenditure) includes your BMR plus the calories burned through daily activities and exercise. TDEE is always higher than BMR.

Is there a way to nudge your BMR higher?

You can increase your BMR by building more muscle mass through strength training, eating enough protein and not severely restricting calories, staying active throughout the day, and getting adequate sleep. Muscle tissue burns more calories at rest than fat tissue, so increasing lean mass raises your BMR.

What happens if you eat under your BMR?

Generally, eating below your BMR is not recommended for extended periods. Consuming fewer calories than your BMR can signal your body to slow its metabolism, conserve energy, and break down muscle tissue. For sustainable weight loss, it is better to eat between your BMR and TDEE, creating a moderate calorie deficit.

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