BMR Calculator – Find Your Basal Metabolic Rate Free

BMR Calculator

Free BMR Calculator
Know Your True Calorie Baseline

Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure using the most scientifically validated formulas. Takes 30 seconds. Zero guesswork.

🔬 Mifflin-St Jeor 📐 Harris-Benedict ⚡ Katch-McArdle 📊 TDEE Breakdown 🥗 Macro Targets

🔬 BMR Calculator

Biological Sex

Age (years)

Weight (kg)

Height (cm)

Height (ft / in)

Body Fat % (optional)

Activity Level

Mifflin-St Jeor (1990) is considered the most accurate formula for most people. It does not require body fat %.

— calories / day (BMR) —

📊 Average BMR by Age Group & Sex

Male

Female

Estimated BMR using Mifflin-St Jeor for average height/weight at each age group. Individual results vary.

What Is BMR — Basal Metabolic Rate?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just to keep you alive. We’re talking about breathing, circulating blood, regulating body temperature, growing and repairing cells, and running every organ system without you lifting a finger. BMR is, in essence, your body’s idle engine speed.

I’ve been working in the nutrition and fitness calculation space for many years, and if there is one number I’d urge every person to know about their body, it is their BMR. Why? Because it forms the foundation of every meaningful calorie target — whether your goal is fat loss, muscle gain, performance, or simply maintaining your current weight without obsessive tracking.

BMR is measured in kilocalories (kcal) per day, which is what most people simply call “calories.” A BMR of 1,800 kcal means your body needs 1,800 calories per day just to exist — zero activity included. Everything you do on top of that (walking, working, exercising) adds to the total.

It’s worth distinguishing BMR from two related terms you’ll encounter:

RMR (Resting Metabolic Rate): Very similar to BMR but measured under slightly less strict conditions (not requiring a full 12-hour fast or perfect lab stillness). RMR values tend to be 10–20 calories higher than BMR. Our calculator uses BMR formulas, which are the more conservative and clinically tested standard.
TDEE (Total Daily Energy Expenditure): Your BMR multiplied by an activity factor. This is your real daily calorie burn when you account for your lifestyle. More on this below.

Why Your BMR Matters More Than You Think

Here’s a pattern I’ve seen repeatedly: someone starts a diet, cuts calories aggressively to 1,200 per day, loses weight initially, then plateaus — frustrated and exhausted. What went wrong? In many cases, they never knew their BMR was 1,600 calories. They were eating below their BMR, which causes metabolic adaptation, muscle loss, hormonal disruption, and unsustainable hunger. The problem was not willpower. It was not knowing the baseline number.

BMR knowledge enables rational, sustainable decisions:

It sets the floor for safe calorie restriction. Eating significantly below your BMR for extended periods harms metabolism, hormones, and muscle mass. Most nutrition professionals recommend never going more than 500–1,000 calories below your TDEE, and never below your BMR except under medical supervision.
It personalizes nutrition. Generic “eat 2,000 calories” advice ignores that a 5’2″ sedentary woman has a TDEE of roughly 1,700 calories and a 6’2″ active man has a TDEE of roughly 3,200 calories. BMR makes nutrition personal.
It evolves with your body. BMR changes with age, body composition shifts, and significant weight changes. Recalculating every 3–6 months keeps your targets accurate.
It anchors every macronutrient calculation. Protein, carbohydrate, and fat targets are all derived from your calorie baseline — which starts with BMR.

How to Use This BMR Calculator

Our BMR calculator is designed to be the most complete free tool available without requiring a gym membership or dietitian appointment. Here’s how to get the most accurate results:

Select your unit system: Choose Metric (kilograms and centimeters) or Imperial (pounds and feet/inches). All conversions are handled automatically.
Select your biological sex: The BMR formulas use sex-specific constants because males and females typically have different lean mass ratios at the same body weight. Use the sex assigned at birth or the one that best reflects your current hormonal and physiological profile.
Enter your age, weight, and height: Use your current measurements, not target values. BMR reflects where you are now.
Enter body fat % (optional): This unlocks the Katch-McArdle formula, which is the most accurate for lean individuals and athletes. If you don’t know your body fat %, leave it blank and use Mifflin-St Jeor.
Select your activity level: Be honest here. Most people overestimate activity. “Moderately active” means genuine exercise 3–5 days per week, not occasional walks.
Choose your formula: Mifflin-St Jeor is recommended for most people. Switch to Katch-McArdle if you have a reliable body fat measurement.
Click “Calculate My BMR”: You’ll receive your BMR, TDEE at your selected activity level, a full TDEE table across all activity levels, and suggested calorie targets for weight loss, maintenance, and gain.

💪 Ready? Jump to the BMR calculator above — your personalized calorie baseline is 30 seconds away.

The Three BMR Formulas Explained

Not all BMR formulas are created equal. Each was developed in a different era, using different population samples and methodologies. Here’s what you need to know about each one:

1. Mifflin-St Jeor (1990) — Recommended for Most People

Developed by MD Mifflin and ST St Jeor and published in the American Journal of Clinical Nutrition, this formula is considered the gold standard by major dietetic associations including the Academy of Nutrition and Dietetics. It was validated on a more diverse, modern population than earlier formulas.

// Mifflin-St Jeor Formula
Male: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
Female: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161

2. Harris-Benedict (Revised 1984) — The Historical Standard

Originally published in 1919 and revised by Roza and Shizgal in 1984, this formula was the dominant clinical standard for decades. It tends to overestimate BMR by approximately 5% compared to modern indirect calorimetry measurements, making Mifflin-St Jeor the preferred choice today. However, Harris-Benedict remains widely used in clinical and research settings.

// Harris-Benedict (Revised 1984)
Male: BMR = (13.397 × weight_kg) + (4.799 × height_cm) − (5.677 × age) + 88.362
Female: BMR = (9.247 × weight_kg) + (3.098 × height_cm) − (4.330 × age) + 447.593

3. Katch-McArdle — Best for Athletes & Lean Individuals

The Katch-McArdle formula bypasses the sex-specific constants of the other formulas and instead calculates BMR directly from lean body mass (LBM). This makes it uniquely accurate for muscular, athletic individuals where standard formulas underestimate BMR due to high lean mass. It requires knowing your body fat percentage.

// Katch-McArdle Formula
LBM = weight_kg × (1 − body_fat_decimal)
BMR = 370 + (21.6 × LBM)

If you’re an athlete or a body composition-focused individual with a reliable DEXA scan or hydrostatic weighing body fat measurement, Katch-McArdle will give you the most precise BMR estimate.

From BMR to TDEE: The Critical Next Step

BMR alone doesn’t tell you how much to eat. Your Total Daily Energy Expenditure (TDEE) does. TDEE is calculated by multiplying your BMR by an activity multiplier — also called the Harris-Benedict activity factor or PAL (Physical Activity Level).

Activity Level	Multiplier	Description	Example
Sedentary	× 1.2	Little to no exercise	Desk job, no gym, occasional walk
Lightly Active	× 1.375	Light exercise 1–3 days/week	Gym 2×/week, active commute
Moderately Active	× 1.55	Moderate exercise 3–5 days/week	Gym 4×/week, moderate cardio
Very Active	× 1.725	Hard exercise 6–7 days/week	Daily training, athletic program
Extra Active	× 1.9	Very hard daily exercise + physical job	Manual labor + daily sport

The most common mistake I see in nutrition coaching is people selecting “Very Active” or “Extra Active” when they train 3–4 days per week at the gym. That is “Moderately Active” territory. Overestimating your activity multiplier means overestimating your TDEE — which means eating more than you burn if your goal is fat loss. The activity level selector should reflect your real lifestyle, not your aspirational one.

BMR for Weight Loss, Gain & Maintenance

Once you know your TDEE, setting your calorie target becomes straightforward. Here are the evidence-based targets used by most registered dietitians and sports nutritionists:

Goal	Calorie Target	Expected Rate	Notes
Aggressive Fat Loss	TDEE − 1,000 kcal	~2 lb/week	Risk of muscle loss; not for beginners
Moderate Fat Loss	TDEE − 500 kcal	~1 lb/week	Sustainable; preserves muscle with protein
Mild Fat Loss	TDEE − 250 kcal	~0.5 lb/week	Best for last 5–10 lbs; minimizes muscle loss
Maintenance	TDEE	Weight stable	Aim here first if new to tracking
Mild Muscle Gain	TDEE + 250 kcal	~0.25–0.5 lb/week	“Lean bulk”; minimizes fat gain
Moderate Muscle Gain	TDEE + 500 kcal	~0.5–1 lb/week	Classic “bulk”; expect some fat gain

⚡ Golden Rule: Never eat below your BMR for extended periods. Sustained sub-BMR eating triggers adaptive thermogenesis — your metabolism slows, muscle breaks down for fuel, and hormones like leptin and T3 drop. Short-term medically supervised very-low-calorie diets are the only exception.

Understanding Macro Targets from Your BMR

Your calorie target is the total. Macronutrients — protein, carbohydrates, and fat — are how you fill that total. Here are the general evidence-based starting points depending on your goal:

Protein — The Non-Negotiable

Protein is the most important macronutrient for body composition regardless of goal. The current research consensus for active individuals is 0.7–1.0g per pound of body weight (1.6–2.2g per kg) per day. During a caloric deficit, higher protein (closer to 1g/lb) helps preserve lean muscle mass significantly. At 4 calories per gram, this forms your protein floor before distributing remaining calories between carbs and fat.

Carbohydrates — Context-Dependent

Carbohydrates are the body’s preferred fuel for high-intensity exercise. Athletes and those with intense training programs benefit from higher carbohydrate intakes (40–50% of total calories). Sedentary individuals or those following low-carb approaches can function well with lower intakes, though very-low-carb diets require adaptation periods and may reduce exercise performance initially.

Fat — The Floor, Not the Ceiling

Dietary fat is essential for hormone production, fat-soluble vitamin absorption, and cellular health. A minimum of approximately 0.3–0.4g per pound of body weight (0.7–0.9g per kg) is recommended regardless of calorie target. Going below this floor while aggressively cutting calories is one of the fastest ways to disrupt hormone function.

Real-World BMR Calculation Examples

Example 1 — 35-Year-Old Male, Moderately Active

Profile: Male, 35 years old, 80 kg, 180 cm, moderately active (gym 4×/week).

Mifflin-St Jeor BMR: (10 × 80) + (6.25 × 180) − (5 × 35) + 5 = 800 + 1,125 − 175 + 5 = 1,755 kcal/day
TDEE: 1,755 × 1.55 = 2,720 kcal/day
For fat loss: 2,720 − 500 = 2,220 kcal/day target.

Example 2 — 28-Year-Old Female, Sedentary

Profile: Female, 28 years old, 65 kg, 163 cm, sedentary (desk job, minimal exercise).

Mifflin-St Jeor BMR: (10 × 65) + (6.25 × 163) − (5 × 28) − 161 = 650 + 1,018.75 − 140 − 161 = 1,368 kcal/day
TDEE: 1,368 × 1.2 = 1,641 kcal/day
For mild fat loss: 1,641 − 250 = 1,391 kcal/day — importantly, still well above her BMR.

Example 3 — Athletic Male, Using Katch-McArdle

Profile: Male, 25 years old, 85 kg, 15% body fat, very active (daily training).

LBM: 85 × (1 − 0.15) = 72.25 kg
Katch-McArdle BMR: 370 + (21.6 × 72.25) = 370 + 1,560.6 = 1,931 kcal/day
TDEE: 1,931 × 1.725 = 3,331 kcal/day
Note: Mifflin-St Jeor would estimate ~2,000 BMR for this profile — Katch-McArdle’s 1,931 is slightly lower but more precise due to accounting for actual lean mass.

BMR Myths That Derail Real People

After years in this field, I’ve encountered the same misconceptions repeatedly. Let me address the most damaging ones directly.

Myth 1: “Eating less always means losing more weight”

This is a dangerous oversimplification. Eating below your BMR for extended periods triggers metabolic adaptation. Your body reduces non-essential physiological functions to conserve energy — reducing thyroid output, lowering NEAT (non-exercise activity thermogenesis), and breaking down muscle tissue. The result is a slower metabolism that makes long-term fat loss progressively harder. Eating at a moderate deficit above your BMR is far more effective long-term.

Myth 2: “My metabolism is just slow — there’s nothing I can do”

True pathologically slow metabolisms (due to conditions like hypothyroidism) exist but are far less common than most people believe. The primary drivers of a “slow” metabolism are usually lower body weight (less mass = fewer calories to maintain), low muscle mass (muscle is metabolically active tissue), chronic dieting history, and low activity levels. All of these are addressable. Resistance training in particular significantly raises BMR over time by increasing lean muscle mass.

Myth 3: “BMR calculators aren’t accurate enough to be useful”

Mifflin-St Jeor has been shown to estimate BMR within ±10% of measured values in most individuals. For practical nutrition planning purposes, that accuracy is entirely sufficient. The bigger source of error in real-world calorie tracking is food logging inaccuracy (studies show people underestimate calorie intake by 20–50% on average) — not the BMR formula.

Myth 4: “Eating small, frequent meals boosts metabolism”

This persistent myth has been thoroughly debunked by controlled research. Meal frequency has no meaningful effect on BMR or total daily calorie burn. What matters for metabolism is total protein intake, total calorie balance, and resistance training — not whether you eat 3 meals or 6. Meal frequency should be chosen based on personal preference and satiety, not metabolic mythology.

Your BMR calculator is most powerful when paired with the right supporting tools. Here are the ones I recommend:

For strength training to increase lean mass and raise your long-term BMR, use the one rep max calculator to structure progressive overload in your resistance training program — muscle is the single best investment you can make in your metabolic rate.
Planning meals and managing nutrition files? Image Converters handles all your document and image format conversions so your nutrition tracking files are always in the right format.
If you’re managing financial goals alongside your fitness journey — including budgeting for quality food and supplements — the gold resale value calculator is a useful asset tracking tool for the financially minded.
For creative wellness content planning and nutrition blog writing, the character headcanon generator can spark ideas for client personas and nutrition education content.
Planning outdoor fitness activities around seasonal disruptions? The snow day calculator helps you anticipate weather-based schedule changes and adjust training accordingly.
For broader business and professional calculations that complement your health-focused lifestyle tracking, Vorici Calculator rounds out the toolkit with specialized computational tools.
For clinical reference on dietary reference intakes and macronutrient recommendations, the National Institute of Diabetes and Digestive and Kidney Diseases provides authoritative guidance on weight management and metabolism.

Frequently Asked Questions About BMR Calculators

What is a normal BMR for a woman?

BMR varies significantly with age, height, and weight, so there’s no single “normal” value. As a general reference, women aged 20–40 with average height and weight typically have BMRs ranging from approximately 1,300 to 1,600 kcal/day using Mifflin-St Jeor. Shorter, lighter, older, or more sedentary women will be at the lower end; taller, heavier, or more muscular women will be higher. Use the calculator above with your actual measurements for a personalized figure.

What is a normal BMR for a man?

Men typically have higher BMRs than women of similar age and weight due to greater average lean muscle mass. A 30–40 year old man of average height and weight will generally have a BMR in the range of 1,600–2,000 kcal/day. Taller, heavier, or more muscular men can exceed 2,200+ kcal/day BMR. Again — use your actual numbers, not population averages.

Which BMR formula is the most accurate?

For the general population, Mifflin-St Jeor (1990) is consistently found to be the most accurate, with studies showing it estimates measured BMR within ±10% for the majority of non-obese adults. For lean athletes with a reliable body fat percentage measurement, Katch-McArdle can be more accurate because it directly accounts for lean body mass. Harris-Benedict tends to overestimate slightly and is considered less accurate than Mifflin-St Jeor for modern populations.

Can I eat at my BMR to lose weight?

Technically yes — since BMR is below your TDEE, eating at your BMR creates a calorie deficit. However, eating at BMR for extended periods is generally not recommended without medical supervision. It risks metabolic adaptation, muscle loss, micronutrient deficiencies, and hormonal disruption. A safer approach is eating 250–500 calories below your TDEE, which creates a sustainable deficit while keeping you well above your BMR.

Does BMR change with age?

Yes — BMR tends to decline with age, primarily due to the gradual loss of muscle mass (sarcopenia) that begins in the late 30s–40s. Each decade after 30, adults lose approximately 3–8% of muscle mass without resistance training intervention. This muscle loss is the main driver of age-related metabolic slowdown, not aging itself. Consistent resistance training throughout life is the most powerful tool for preserving BMR as you age.

How often should I recalculate my BMR?

Recalculate your BMR whenever your weight changes by more than 5–10 lbs (2–4 kg), after a significant body recomposition period (e.g., gaining significant muscle or losing significant fat), every 6 months as a general check-in, or whenever your activity level changes substantially. Your calorie targets should be a moving baseline that tracks your changing body, not a fixed number set years ago.

Is BMR the same as metabolism?

BMR is one component of your total metabolism. Your complete metabolic picture (TDEE) includes BMR (about 60–70% of total), the Thermic Effect of Food or TEF (about 10% — calories burned digesting food), Non-Exercise Activity Thermogenesis or NEAT (about 15–30% — all movement outside formal exercise), and Exercise Activity Thermogenesis (calories burned during structured exercise). BMR is the biggest single component, which is why it’s the right starting point for any nutrition calculation.

Why does this calculator ask for body fat percentage?

Body fat percentage is required for the Katch-McArdle formula, which calculates BMR from lean body mass (total weight minus fat mass). This makes it more accurate for muscular individuals, where standard formulas that only use total body weight tend to underestimate BMR. If you don’t have a reliable body fat measurement, leave the field blank and use Mifflin-St Jeor — it doesn’t require body fat % and is accurate for most people.

🌿 Found this BMR calculator and guide helpful? Bookmark it and recalculate every time your weight or activity changes. Your body is always evolving — your calorie targets should too.

Last updated: April 2025. Formulas and nutritional guidance reflect peer-reviewed scientific literature as of publication. This tool provides estimates for informational purposes only and does not constitute medical or dietary advice. Consult a registered dietitian or physician for personalized nutrition guidance.

Free BMR CalculatorKnow Your True Calorie Baseline