What is a normal BMR for a 30-year-old woman?

For a 30-year-old woman at average height (163 cm) and weight (65 kg), the Mifflin-St Jeor formula gives a BMR of approximately 1,440 calories per day. With moderate activity (3-4 days/week exercise), her TDEE is approximately 1,440 x 1.55 = 2,232 calories/day. BMR typically ranges from 1,300 to 1,600 calories for most adult women.

BMR Calculator

Q: What is the difference between BMR and TDEE?

BMR is your calorie burn at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for movement, exercise, and daily activity. TDEE is the more useful number for setting calorie targets because it reflects your actual daily energy need.

Q: Which BMR formula is most accurate - Mifflin-St Jeor or Harris-Benedict?

Research consistently shows that the Mifflin-St Jeor equation (1990) is more accurate than the original Harris-Benedict equation (1919) for most modern adults. A 2005 study in the Journal of the American Dietetic Association found Mifflin-St Jeor predicted RMR within 10% for 82% of subjects, compared to 72% for Harris-Benedict. This calculator uses Mifflin-St Jeor.

Q: How does age affect BMR?

BMR naturally declines with age, primarily due to loss of lean muscle mass (sarcopenia). Research suggests BMR decreases by roughly 1-2% per decade after age 30. The best way to counteract this decline is resistance training, which preserves muscle mass and keeps metabolic rate higher as you age.

Find your daily calorie burn at rest (BMR) and total daily energy expenditure (TDEE).

Age

years

Weight

Height

Weight

Height

ft in

Activity Level

BMR

—

calories / day at rest

TDEE (Maintenance)

—

calories / day

Weight Loss Target

—

−500 cal/day

Weight Gain Target

—

+500 cal/day

🔥 What is BMR?

Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to sustain essential life functions while at complete rest - in a warm environment, in a post-absorptive state, and not engaged in any physical activity. These essential functions include breathing, blood circulation, maintaining body temperature, cell production, protein synthesis, and the constant operation of organs such as the heart, liver, kidneys, and brain.

BMR is often confused with Resting Metabolic Rate (RMR), which is slightly higher because RMR is measured under less strict conditions. In practical terms, the two values are close enough that they are used interchangeably in most nutrition and fitness contexts.

Understanding your BMR is the first step in accurately determining your total daily calorie needs. Once you know your BMR, you multiply it by an activity factor to get your Total Daily Energy Expenditure (TDEE) - the number of calories you need each day accounting for your actual movement and exercise. This TDEE figure is the single most important number for designing an effective diet for weight loss, maintenance, or muscle gain.

The most widely validated formula for estimating BMR is the Mifflin-St Jeor equation, developed in 1990 and shown to be accurate within 10% for most adults. It accounts for weight, height, age, and biological sex. This calculator uses Mifflin-St Jeor as its primary formula because research consistently shows it outperforms the older Harris-Benedict equation in predicting actual resting energy expenditure.

Factors that influence BMR include body composition (more muscle = higher BMR), age (BMR declines gradually with age), sex (males generally have higher BMR due to greater muscle mass), genetics, hormonal status (thyroid function in particular), and ambient temperature. BMR is not fixed - it responds to changes in body composition and metabolic health over time.

📐 BMR Formula (Mifflin-St Jeor)

Men: BMR = (10 × W) + (6.25 × H) − (5 × A) + 5

Women: BMR = (10 × W) + (6.25 × H) − (5 × A) − 161

W = Weight in kilograms (kg)

H = Height in centimetres (cm)

A = Age in years

To calculate TDEE, multiply BMR by the appropriate activity factor:

TDEE = BMR × Activity Factor

Sedentary (desk job, no exercise) = × 1.2

Lightly Active (1–3 days/week) = × 1.375

Moderately Active (3–5 days/week) = × 1.55

Very Active (6–7 days/week) = × 1.725

Extra Active (physical job + hard exercise) = × 1.9

📖 How to Use This Calculator

Steps to Calculate Your BMR and TDEE

Select your gender - Male or Female - using the tabs at the top. The Mifflin-St Jeor formula has different constants for each.

Choose your unit system - Metric (kg and cm) or Imperial (lb, ft, in).

Enter your age, weight, and height accurately. Use your morning weight without shoes for the most consistent results.

Select your activity level honestly. Most office workers should choose Sedentary or Lightly Active. Overestimating activity is the most common source of error in calorie calculations.

Click Calculate BMR to see your BMR, TDEE, and recommended calorie targets for weight loss or gain.

💡 Example Calculations

Example 1 — 35-year-old Male, 80 kg, 178 cm, Moderately Active

BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5 = 800 + 1112.5 − 175 + 5 = 1,742.5 cal/day

TDEE = 1,742.5 × 1.55 (moderately active) = 2,701 cal/day

Weight loss target: 2,701 − 500 = 2,201 cal/day | Weight gain: 3,201 cal/day

Try this example →

Example 2 — 28-year-old Female, 60 kg, 163 cm, Lightly Active

BMR = (10 × 60) + (6.25 × 163) − (5 × 28) − 161 = 600 + 1018.75 − 140 − 161 = 1,317.75 cal/day

TDEE = 1,317.75 × 1.375 = 1,812 cal/day

Weight loss target: 1,812 − 500 = 1,312 cal/day | Maintenance: 1,812 cal/day

Try this example →

❓ Frequently Asked Questions

What is BMR and why does it matter?+

BMR (Basal Metabolic Rate) is the number of calories your body needs to sustain basic physiological functions - breathing, circulation, cell repair, and temperature regulation - while at complete rest. It matters because it forms the foundation of your total daily energy expenditure (TDEE). If you consume fewer calories than your TDEE, you lose weight; more, you gain weight. Without knowing your BMR, calorie targets are just guesses.

What is the difference between BMR and TDEE?+

BMR is your calorie burn at complete rest - as if you lay in bed all day. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for your actual movement, exercise, and daily lifestyle. TDEE is the more useful number for setting calorie targets because it reflects your true daily energy need. Most people's TDEE is 1.4–1.8× their BMR.

Which BMR formula is most accurate - Mifflin-St Jeor or Harris-Benedict?+

Research consistently shows the Mifflin-St Jeor equation (1990) is more accurate than the original Harris-Benedict equation (1919) for most modern adults. A 2005 study in the Journal of the American Dietetic Association found Mifflin-St Jeor predicted resting metabolic rate within 10% for 82% of subjects, compared to 72% for Harris-Benedict. This calculator uses Mifflin-St Jeor as the primary formula.

How do I use BMR to lose weight?+

Calculate your TDEE using your BMR and activity level. Then subtract 300–500 calories from your TDEE to create a moderate deficit. This typically results in 0.3–0.5 kg of weight loss per week - a safe, sustainable rate. Avoid cutting more than 500 calories below TDEE without medical guidance, as extreme deficits slow metabolism and cause muscle loss.

Does BMR change with age?+

Yes. BMR naturally declines with age, primarily because muscle mass decreases after the mid-30s (sarcopenia). Research suggests BMR drops about 1–2% per decade after age 20. Regular strength training and adequate protein intake (1.6–2.2 g per kg of body weight) are the most effective strategies to slow this decline by preserving muscle mass.

What is the thermic effect of food and does it affect BMR?+

The thermic effect of food (TEF) is the energy your body uses to digest, absorb, and metabolise food - typically 8–10% of total daily calories. Protein has the highest TEF (20–35%), carbohydrates moderate (5–10%), and fats the lowest (0–3%). TEF is separate from BMR (which is measured in a post-absorptive fasted state) and is one component of TDEE. High-protein diets increase TDEE slightly through a higher TEF compared to high-fat or high-carb diets of equal calories.

Can I use BMR to calculate how many calories I need to maintain weight?+

BMR is just the base - multiply by an activity factor to get TDEE (Total Daily Energy Expenditure). Sedentary (desk job, no exercise): BMR x 1.2. Lightly active (1-3 days/week exercise): BMR x 1.375. Moderately active (3-5 days): BMR x 1.55. Very active (6-7 days hard exercise): BMR x 1.725. Eat at TDEE to maintain weight, below to lose, above to gain.

How accurate is the Mifflin-St Jeor equation?+

The Mifflin-St Jeor equation (1990) is the most widely validated BMR formula for modern populations. Studies show it estimates BMR within 10% for about 80% of adults. It is more accurate than the older Harris-Benedict equation (1919), which tends to overestimate BMR by 5-15%. For highly muscular individuals or those with unusual body compositions, indirect calorimetry (metabolic testing) provides a more accurate measurement.

How does age affect BMR?+

BMR declines approximately 1-2% per decade after age 20, primarily due to loss of muscle mass (sarcopenia). A 60-year-old may have a BMR 15-20% lower than a 20-year-old of the same height and weight. Resistance training can partially offset this by preserving or building muscle mass. This is why calorie needs generally decrease with age even without changes in activity level.

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📌 Quick Tips

💡Your BMR accounts for roughly 60–75% of your total daily calorie burn. Even at rest, your body needs energy to breathe, pump blood, and maintain organ function.

💡Muscle is metabolically active tissue. Building muscle through strength training gradually raises your BMR, making it easier to manage weight long-term.

💡Crash diets and severe calorie restriction can lower your BMR over time as the body adapts to conserve energy. A moderate deficit of 300–500 calories is more sustainable.