Resting Metabolic Rate Calculator

Find out how many calories your body burns at complete rest — the foundation of every smart nutrition plan.

Biological Sex

Unit System

Age (years)

Please enter a valid age between 1 and 120.

Weight (kg)

Enter a valid weight.

Height (cm)

Enter a valid height.

Activity Level (for TDEE)

Your Resting Metabolic Rate

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calories / day

Where you fall on the RMR spectrum:

Very Low
<1,000 Low
1,000–1,400 Average
1,400–2,000 High
2,000–2,600 Very High
>2,600

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Daily Calorie Targets

Goal	Calories/Day

Formula Comparison

Macro Breakdown (based on TDEE)

Macro	Grams/Day	Calories

Based on a balanced 30% protein / 40% carbs / 30% fat split from your TDEE.

⚠ Disclaimer: This tool is for informational purposes only. Consult a healthcare professional for medical advice. Individual metabolic rates can vary significantly from formula-based estimates.

How to Use This Resting Metabolic Rate Calculator

Enter your biological sex, age, height, and weight — then pick your typical activity level. Hit "Calculate My RMR" to instantly see how many calories your body burns at complete rest, your Total Daily Energy Expenditure (TDEE), and your personalized calorie targets for weight loss, maintenance, or gain.

Switch between Metric (kg/cm) and Imperial (lbs/inches) units at any time. The formula comparison tab shows you results from three leading RMR equations side by side.

Why This Matters

Your Resting Metabolic Rate is the single biggest piece of the calorie-balance puzzle. For most people, RMR accounts for 60–75% of total daily energy expenditure — meaning the majority of the calories you burn happen while you're just sitting still, breathing, and keeping your organs running.

Here's why this number is so powerful: a 35-year-old woman, 165 cm, 65 kg has an RMR of roughly 1,430 kcal/day. If she eats 1,200 kcal (a common "diet" target), she's actually eating below her resting needs — triggering metabolic adaptation, muscle loss, and fatigue. Knowing your RMR prevents that mistake.

Fitness coaches use RMR to set safe minimum calorie floors for clients. Registered dietitians use it to structure sustainable meal plans. Athletes use it to avoid under-fueling during training blocks. And anyone tracking weight loss uses it to understand why eating less than ~500 kcal below TDEE is usually the sweet spot for fat loss without metabolic damage.

If you've ever hit a weight-loss plateau, been constantly fatigued on a diet, or gained fat despite "eating healthy," your actual RMR is likely the missing variable.

How It's Calculated

This calculator defaults to the Mifflin-St Jeor equation, which most dietitians consider the most accurate for the general population (within ±10% of measured RMR in research studies):

Men: RMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: RMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

We also show the original Harris-Benedict (1919, revised 1984) and the Katch-McArdle formula (which accounts for lean body mass, estimated at ~80% of body weight if body fat isn't entered). TDEE is calculated by multiplying your RMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active).

Tips & Common Mistakes

Don't eat below your RMR. Consistently eating below your resting calorie needs causes muscle loss and metabolic slowdown. Most health guidelines recommend a minimum of 1,200 kcal (women) or 1,500 kcal (men) regardless of RMR.
Use TDEE, not RMR, as your baseline. RMR is what you burn at rest — TDEE is what you actually burn living your life. Start from TDEE when setting calorie goals.
Activity levels are easy to overestimate. Most gym-goers who exercise 3–4x/week and sit at a desk fall into "Lightly Active," not "Moderately Active."
RMR changes with age and muscle mass. Muscle tissue burns ~6 kcal/kg/day at rest versus ~2 kcal/kg/day for fat tissue. Strength training can meaningfully raise your RMR over time.
Formula results are estimates. True RMR requires indirect calorimetry in a clinical setting. These formulas are accurate within ±10–15% for most healthy adults but can vary more for very lean athletes or individuals with thyroid conditions.

Frequently Asked Questions

What's the difference between RMR and BMR?

Basal Metabolic Rate (BMR) is measured under very strict laboratory conditions — fasted overnight, lying still in a thermoneutral environment. Resting Metabolic Rate (RMR) is measured under more relaxed conditions and is typically 10–20% higher than BMR. In practice, the terms are often used interchangeably, and the difference rarely matters for day-to-day nutrition planning.

Why is my RMR higher or lower than a friend's who weighs the same?

Body composition plays a huge role — someone with more lean muscle mass will have a higher RMR even at the same body weight because muscle is metabolically active tissue. Age, hormonal factors (thyroid, testosterone, estrogen), genetics, and even ambient temperature can influence your actual metabolic rate. Two people of the same weight, height, and age can have RMRs that differ by 200–300+ calories per day.

How do I use my RMR to lose weight?

Start with your TDEE (RMR × activity factor) and subtract 300–500 calories to create a moderate deficit. This pace typically produces 0.5–1 lb of fat loss per week. Going more aggressive than 500 kcal below TDEE risks muscle loss, fatigue, and metabolic adaptation. If weight loss stalls after 2–3 weeks, a small calorie adjustment or a "diet break" week at maintenance can help reset your metabolism.

Which formula should I trust — Mifflin, Harris-Benedict, or Katch-McArdle?

For most people, Mifflin-St Jeor is the most validated in modern research and is the default recommendation from the Academy of Nutrition and Dietetics. Harris-Benedict (revised) is also widely used and generally within 5% of Mifflin. Katch-McArdle is theoretically the most accurate if you know your body fat percentage, because it uses lean body mass. If you've had a DEXA scan or accurate body fat measurement, Katch-McArdle may give you a better estimate.