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BMR Calculator

Calculate your Basal Metabolic Rate — the number of calories your body needs at complete rest to maintain basic physiological functions such as breathing, circulation, and cellular repair.
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BMR Calculator – ToolPremier
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Sex
Optional — enables the Katch-McArdle formula

ToolPremier · BMR Calculator · All calculations are performed locally — no data is sent anywhere.

How it works

Calculate your BMR in three steps

1. Enter your details

Provide your age, sex, height, and weight. These four variables are the standard inputs used by BMR formulas to estimate resting energy expenditure.

2. Choose your formula

Select between the Mifflin–St Jeor equation (recommended for most people) or the Harris–Benedict equation (older but still widely cited). Results may differ slightly between the two.

3. View your BMR

The output shows how many calories per day your body burns at complete rest, forming the foundation for calculating your total daily calorie needs.

FAQ

Common questions

Basal Metabolic Rate (BMR) is the minimum number of calories your body requires to keep essential functions running — heartbeat, breathing, body temperature regulation, and cellular repair — while at complete rest and in a fasted state. It represents roughly 60–75% of most people’s total daily calorie burn. TDEE (Total Daily Energy Expenditure) builds on BMR by adding the energy used during physical activity, digestion, and non-exercise movement. BMR is the baseline figure; TDEE is the more practical daily target for nutrition planning.
The Mifflin–St Jeor equation (developed in 1990) is generally considered more accurate for modern populations than the original Harris–Benedict equation (1919). Several validation studies have found that Mifflin–St Jeor predicts resting metabolic rate within 10% for the majority of adults. The Katch–McArdle formula uses lean body mass rather than total weight, which may improve accuracy for individuals who know their body fat percentage. No single formula is perfectly accurate for everyone due to natural metabolic variability between individuals.
On average, men have a higher BMR than women of the same age and weight. This is largely because men tend to have greater muscle mass and less body fat relative to their total weight, and muscle tissue burns more calories at rest than fat tissue. Hormonal differences also play a role. These are population-level averages built into the formulas — individual BMR varies considerably, and the formula result is always an estimate rather than a precise measurement.
BMR declines naturally with age, primarily due to the gradual loss of muscle mass (sarcopenia). The most effective way to maintain or modestly increase BMR is resistance training, which helps preserve or build metabolically active muscle tissue. Severe calorie restriction can significantly lower BMR through metabolic adaptation, which is one reason aggressive crash diets are difficult to sustain and often lead to rebound weight gain. Adequate protein intake, quality sleep, and thyroid health also influence resting metabolic rate.

Keep going

Related tools

TDEE Calculator

Multiply your BMR by your activity level to get your total daily calorie needs.

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Calorie Deficit Calculator

Use your BMR as the foundation for calculating a safe daily calorie deficit.

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Macro Calculator

Break your daily calorie target into protein, carbohydrate, and fat goals.

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BMI Calculator

Assess your weight classification alongside your metabolic data.

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About the BMR Calculator

The BMR Calculator estimates the number of calories your body burns at rest, providing the foundation for any calorie-based nutrition plan. It is widely used by fitness enthusiasts, registered dietitians, and healthcare providers as a starting point for setting daily calorie targets. BMR is influenced by age, sex, height, weight, and body composition, and understanding it helps avoid both chronic over-eating and excessive restriction.

Benefits

  • Supports two validated formulas: Mifflin–St Jeor and Harris–Benedict, with results shown side by side
  • Works with both metric (kg/cm) and imperial (lbs/ft/in) unit inputs
  • Explains clearly what the BMR figure means and how to use it for nutrition planning
  • Instant browser-based calculation with no data storage or account requirement

Privacy

Your age, weight, height, and sex are processed entirely within your browser and are never transmitted to any server or stored in any form.